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640 lines
21 KiB
C++
640 lines
21 KiB
C++
/*
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* Copyright (c) 2023 the ThorVG project. All rights reserved.
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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//
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// gif.h
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// by Charlie Tangora
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// Public domain.
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// Email me : ctangora -at- gmail -dot- com
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//
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// This file offers a simple, very limited way to create animated GIFs directly in code.
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//
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// Those looking for particular cleverness are likely to be disappointed; it's pretty
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// much a straight-ahead implementation of the GIF format with optional Floyd-Steinberg
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// dithering. (It does at least use delta encoding - only the changed portions of each
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// frame are saved.)
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//
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// So resulting files are often quite large. The hope is that it will be handy nonetheless
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// as a quick and easily-integrated way for programs to spit out animations.
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//
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// Only RGBA8 is currently supported as an input format. (The alpha is ignored.)
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//
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// USAGE:
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// Create a GifWriter struct. Pass it to GifBegin() to initialize and write the header.
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// Pass subsequent frames to GifWriteFrame().
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// Finally, call GifEnd() to close the file handle and free memory.
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//
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#include <memory.h>
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#include "tvgMath.h"
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#include "tvgGifEncoder.h"
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#define TRANSPARENT_IDX 0
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typedef struct
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{
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int bitDepth;
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uint8_t r[256];
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uint8_t g[256];
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uint8_t b[256];
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// k-d tree over RGB space, organized in heap fashion
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// i.e. left child of node i is node i*2, right child is node i*2+1
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// nodes 256-511 are implicitly the leaves, containing a color
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uint8_t treeSplitElt[256];
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uint8_t treeSplit[256];
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} GifPalette;
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// Simple structure to write out the LZW-compressed portion of the image
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// one bit at a time
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typedef struct
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{
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uint8_t bitIndex; // how many bits in the partial byte written so far
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uint8_t byte; // current partial byte
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uint32_t chunkIndex;
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uint8_t chunk[256]; // bytes are written in here until we have 256 of them, then written to the file
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} GifBitStatus;
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// The LZW dictionary is a 256-ary tree constructed as the file is encoded,
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// this is one node
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typedef struct
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{
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uint16_t m_next[256];
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} GifLzwNode;
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/************************************************************************/
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/* Internal Class Implementation */
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/************************************************************************/
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// walks the k-d tree to pick the palette entry for a desired color.
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// Takes as in/out parameters the current best color and its error -
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// only changes them if it finds a better color in its subtree.
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// this is the major hotspot in the code at the moment.
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static void _getClosestPaletteColor( GifPalette* pPal, int r, int g, int b, int* bestInd, int* bestDiff, int treeRoot )
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{
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// base case, reached the bottom of the tree
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if(treeRoot > (1<<pPal->bitDepth)-1) {
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int ind = treeRoot-(1<<pPal->bitDepth);
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if(ind == TRANSPARENT_IDX) return;
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// check whether this color is better than the current winner
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int r_err = r - ((int32_t)pPal->r[ind]);
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int g_err = g - ((int32_t)pPal->g[ind]);
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int b_err = b - ((int32_t)pPal->b[ind]);
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int diff = abs(r_err)+ abs(g_err) + abs(b_err);
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if(diff < *bestDiff) {
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*bestInd = ind;
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*bestDiff = diff;
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}
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return;
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}
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// take the appropriate color (r, g, or b) for this node of the k-d tree
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int comps[3]; comps[0] = r; comps[1] = g; comps[2] = b;
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int splitComp = comps[pPal->treeSplitElt[treeRoot]];
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int splitPos = pPal->treeSplit[treeRoot];
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if (splitPos > splitComp) {
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// check the left subtree
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_getClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2);
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if (*bestDiff > splitPos - splitComp) {
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// cannot prove there's not a better value in the right subtree, check that too
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_getClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2+1);
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}
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} else {
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_getClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2+1);
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if (*bestDiff > splitComp - splitPos) {
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_getClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2);
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}
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}
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}
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static void _swapPixels(uint8_t* image, int pixA, int pixB)
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{
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uint8_t rA = image[pixA*4];
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uint8_t gA = image[pixA*4+1];
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uint8_t bA = image[pixA*4+2];
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uint8_t aA = image[pixA*4+3];
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uint8_t rB = image[pixB*4];
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uint8_t gB = image[pixB*4+1];
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uint8_t bB = image[pixB*4+2];
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uint8_t aB = image[pixA*4+3];
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image[pixA*4] = rB;
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image[pixA*4+1] = gB;
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image[pixA*4+2] = bB;
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image[pixA*4+3] = aB;
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image[pixB*4] = rA;
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image[pixB*4+1] = gA;
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image[pixB*4+2] = bA;
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image[pixB*4+3] = aA;
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}
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// just the partition operation from quicksort
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static int _partition(uint8_t* image, const int left, const int right, const int elt, int pivotIndex)
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{
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const int pivotValue = image[(pivotIndex)*4+elt];
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_swapPixels(image, pivotIndex, right-1);
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int storeIndex = left;
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bool split = 0;
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for (int ii = left; ii < right - 1; ++ii) {
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int arrayVal = image[ii*4+elt];
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if(arrayVal < pivotValue) {
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_swapPixels(image, ii, storeIndex);
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++storeIndex;
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} else if(arrayVal == pivotValue) {
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if (split) {
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_swapPixels(image, ii, storeIndex);
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++storeIndex;
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}
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split = !split;
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}
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}
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_swapPixels(image, storeIndex, right-1);
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return storeIndex;
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}
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// Perform an incomplete sort, finding all elements above and below the desired median
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static void _partitionByMedian(uint8_t* image, int left, int right, int com, int neededCenter)
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{
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if (left < right-1) {
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int pivotIndex = left + (right-left)/2;
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pivotIndex = _partition(image, left, right, com, pivotIndex);
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// Only "sort" the section of the array that contains the median
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if(pivotIndex > neededCenter) _partitionByMedian(image, left, pivotIndex, com, neededCenter);
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if(pivotIndex < neededCenter) _partitionByMedian(image, pivotIndex+1, right, com, neededCenter);
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}
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}
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// Builds a palette by creating a balanced k-d tree of all pixels in the image
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static void _splitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, int splitElt, int splitDist, int treeNode, GifPalette* pal)
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{
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if(lastElt <= firstElt || numPixels == 0) return;
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// base case, bottom of the tree
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if (lastElt == firstElt + 1) {
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// otherwise, take the average of all colors in this subcube
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uint64_t r=0, g=0, b=0;
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for(int ii=0; ii<numPixels; ++ii) {
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r += image[ii*4+0];
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g += image[ii*4+1];
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b += image[ii*4+2];
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}
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r += (uint64_t)numPixels / 2; // round to nearest
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g += (uint64_t)numPixels / 2;
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b += (uint64_t)numPixels / 2;
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r /= (uint64_t)numPixels;
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g /= (uint64_t)numPixels;
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b /= (uint64_t)numPixels;
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pal->r[firstElt] = (uint8_t)r;
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pal->g[firstElt] = (uint8_t)g;
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pal->b[firstElt] = (uint8_t)b;
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return;
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}
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// Find the axis with the largest range
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int minR = 255, maxR = 0;
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int minG = 255, maxG = 0;
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int minB = 255, maxB = 0;
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for (int ii=0; ii<numPixels; ++ii) {
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int r = image[ii*4+0];
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int g = image[ii*4+1];
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int b = image[ii*4+2];
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if(r > maxR) maxR = r;
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if(r < minR) minR = r;
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if(g > maxG) maxG = g;
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if(g < minG) minG = g;
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if(b > maxB) maxB = b;
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if(b < minB) minB = b;
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}
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int rRange = maxR - minR;
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int gRange = maxG - minG;
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int bRange = maxB - minB;
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// and split along that axis. (incidentally, this means this isn't a "proper" k-d tree but I don't know what else to call it)
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int splitCom = 1;
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if (bRange > gRange) splitCom = 2;
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if (rRange > bRange && rRange > gRange) splitCom = 0;
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int subPixelsA = numPixels * (splitElt - firstElt) / (lastElt - firstElt);
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int subPixelsB = numPixels-subPixelsA;
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_partitionByMedian(image, 0, numPixels, splitCom, subPixelsA);
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pal->treeSplitElt[treeNode] = (uint8_t)splitCom;
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pal->treeSplit[treeNode] = image[subPixelsA*4+splitCom];
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_splitPalette(image, subPixelsA, firstElt, splitElt, splitElt-splitDist, splitDist/2, treeNode*2, pal);
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_splitPalette(image+subPixelsA*4, subPixelsB, splitElt, lastElt, splitElt+splitDist, splitDist/2, treeNode*2+1, pal);
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}
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// Finds all pixels that have changed from the previous image and
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// moves them to the from of the buffer.
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// This allows us to build a palette optimized for the colors of the
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// changed pixels only.
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static int _pickChangedPixels(const uint8_t* lastFrame, uint8_t* frame, int numPixels, bool transparent)
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{
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int numChanged = 0;
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uint8_t* writeIter = frame;
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for (int ii=0; ii < numPixels; ++ii) {
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if (frame[3] == 255) {
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if (transparent || (lastFrame[0] != frame[0] || lastFrame[1] != frame[1] || lastFrame[2] != frame[2])) {
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writeIter[0] = frame[0];
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writeIter[1] = frame[1];
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writeIter[2] = frame[2];
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++numChanged;
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writeIter += 4;
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}
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}
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lastFrame += 4;
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frame += 4;
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}
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return numChanged;
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}
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// Creates a palette by placing all the image pixels in a k-d tree and then averaging the blocks at the bottom.
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// This is known as the "modified median split" technique
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static void _makePalette(GifWriter* writer, const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_t width, uint32_t height, int bitDepth, GifPalette* pPal, bool transparent)
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{
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pPal->bitDepth = bitDepth;
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size_t imageSize = (size_t)(width * height * 4 * sizeof(uint8_t));
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memcpy(writer->tmpImage, nextFrame, imageSize);
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int numPixels = (int)(width * height);
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if (lastFrame) numPixels = _pickChangedPixels(lastFrame, writer->tmpImage, numPixels, transparent);
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const int lastElt = 1 << bitDepth;
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const int splitElt = lastElt/2;
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const int splitDist = splitElt/2;
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_splitPalette(writer->tmpImage, numPixels, 1, lastElt, splitElt, splitDist, 1, pPal);
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// add the bottom node for the transparency index
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pPal->treeSplit[1 << (bitDepth-1)] = 0;
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pPal->treeSplitElt[1 << (bitDepth-1)] = 0;
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pPal->r[0] = pPal->g[0] = pPal->b[0] = 0;
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}
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void _palettizePixel(const uint8_t* nextFrame, uint8_t* outFrame, GifPalette* pPal)
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{
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int32_t bestDiff = 1000000;
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int32_t bestInd = 1;
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_getClosestPaletteColor(pPal, nextFrame[0], nextFrame[1], nextFrame[2], &bestInd, &bestDiff, 1);
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// Write the resulting color to the output buffer
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outFrame[0] = pPal->r[bestInd];
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outFrame[1] = pPal->g[bestInd];
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outFrame[2] = pPal->b[bestInd];
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outFrame[3] = (uint8_t)bestInd;
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}
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// Picks palette colors for the image using simple thresholding, no dithering
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static void _thresholdImage(const uint8_t* lastFrame, const uint8_t* nextFrame, uint8_t* outFrame, uint32_t width, uint32_t height, GifPalette* pPal, bool transparent)
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{
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uint32_t numPixels = width*height;
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if (transparent) {
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for (uint32_t ii = 0; ii < numPixels; ++ii) {
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if (nextFrame[3] < 255) {
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outFrame[0] = 0;
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outFrame[1] = 0;
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outFrame[2] = 0;
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outFrame[3] = TRANSPARENT_IDX;
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} else {
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_palettizePixel(nextFrame, outFrame, pPal);
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}
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if (lastFrame) lastFrame += 4;
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outFrame += 4;
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nextFrame += 4;
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}
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} else {
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for (uint32_t ii = 0; ii < numPixels; ++ii) {
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// if a previous color is available, and it matches the current color,
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// set the pixel to transparent
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if(lastFrame && lastFrame[0] == nextFrame[0] && lastFrame[1] == nextFrame[1] && lastFrame[2] == nextFrame[2]) {
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outFrame[0] = lastFrame[0];
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outFrame[1] = lastFrame[1];
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outFrame[2] = lastFrame[2];
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outFrame[3] = TRANSPARENT_IDX;
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} else {
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_palettizePixel(nextFrame, outFrame, pPal);
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}
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if (lastFrame) lastFrame += 4;
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outFrame += 4;
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nextFrame += 4;
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}
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}
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}
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// insert a single bit
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static void _writeBit(GifBitStatus* stat, uint32_t bit)
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{
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bit = bit & 1;
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bit = bit << stat->bitIndex;
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stat->byte |= bit;
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++stat->bitIndex;
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if (stat->bitIndex > 7) {
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// move the newly-finished byte to the chunk buffer
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stat->chunk[stat->chunkIndex++] = stat->byte;
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// and start a new byte
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stat->bitIndex = 0;
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stat->byte = 0;
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}
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}
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// write all bytes so far to the file
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static void _writeChunk(FILE* f, GifBitStatus* stat)
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{
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fputc((int)stat->chunkIndex, f);
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fwrite(stat->chunk, 1, stat->chunkIndex, f);
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stat->bitIndex = 0;
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stat->byte = 0;
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stat->chunkIndex = 0;
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}
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static void _writeCode(FILE* f, GifBitStatus* stat, uint32_t code, uint32_t length)
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{
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for (uint32_t ii = 0; ii < length; ++ii) {
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_writeBit(stat, code);
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code = code >> 1;
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if (stat->chunkIndex == 255) _writeChunk(f, stat);
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}
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}
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// write a 256-color (8-bit) image palette to the file
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static void _writePalette(const GifPalette* pPal, FILE* f)
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{
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fputc(0, f); // first color: transparency
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fputc(0, f);
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fputc(0, f);
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for (int ii = 1; ii < (1 << pPal->bitDepth); ++ii) {
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uint32_t r = pPal->r[ii];
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uint32_t g = pPal->g[ii];
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uint32_t b = pPal->b[ii];
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fputc((int)r, f);
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fputc((int)g, f);
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fputc((int)b, f);
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}
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}
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// write the image header, LZW-compress and write out the image
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static void _writeLzwImage(FILE* f, uint8_t* image, uint32_t left, uint32_t top, uint32_t width, uint32_t height, uint32_t delay, GifPalette* pPal, bool transparent)
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{
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// graphics control extension
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fputc(0x21, f);
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fputc(0xf9, f);
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fputc(0x04, f);
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fputc((transparent ? 0x09 : 0x05), f); //clear prev frame or not.
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fputc(delay & 0xff, f);
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fputc((delay >> 8) & 0xff, f);
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fputc(TRANSPARENT_IDX, f); // transparent color index
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fputc(0, f);
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fputc(0x2c, f); // image descriptor block
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fputc(left & 0xff, f); // corner of image in canvas space
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fputc((left >> 8) & 0xff, f);
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fputc(top & 0xff, f);
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fputc((top >> 8) & 0xff, f);
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fputc(width & 0xff, f); // width and height of image
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fputc((width >> 8) & 0xff, f);
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fputc(height & 0xff, f);
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fputc((height >> 8) & 0xff, f);
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//fputc(0, f); // no local color table, no transparency
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//fputc(0x80, f); // no local color table, but transparency
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fputc(0x80 + pPal->bitDepth-1, f); // local color table present, 2 ^ bitDepth entries
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_writePalette(pPal, f);
|
|
|
|
const int minCodeSize = pPal->bitDepth;
|
|
const uint32_t clearCode = 1 << pPal->bitDepth;
|
|
|
|
fputc(minCodeSize, f); // min code size 8 bits
|
|
|
|
GifLzwNode* codetree = (GifLzwNode*)malloc(sizeof(GifLzwNode)*4096);
|
|
|
|
memset(codetree, 0, sizeof(GifLzwNode)*4096);
|
|
int32_t curCode = -1;
|
|
uint32_t codeSize = (uint32_t)minCodeSize + 1;
|
|
uint32_t maxCode = clearCode+1;
|
|
|
|
GifBitStatus stat;
|
|
stat.byte = 0;
|
|
stat.bitIndex = 0;
|
|
stat.chunkIndex = 0;
|
|
|
|
_writeCode(f, &stat, clearCode, codeSize); // start with a fresh LZW dictionary
|
|
|
|
for (uint32_t yy = 0; yy < height; ++yy) {
|
|
for (uint32_t xx=0; xx<width; ++xx) {
|
|
// top-left origin
|
|
uint8_t nextValue = image[(yy*width+xx)*4+3];
|
|
|
|
// "loser mode" - no compression, every single code is followed immediately by a clear
|
|
//WriteCode( f, stat, nextValue, codeSize );
|
|
//WriteCode( f, stat, 256, codeSize );
|
|
|
|
if (curCode < 0) {
|
|
// first value in a new run
|
|
curCode = nextValue;
|
|
} else if (codetree[curCode].m_next[nextValue]) {
|
|
// current run already in the dictionary
|
|
curCode = codetree[curCode].m_next[nextValue];
|
|
} else {
|
|
// finish the current run, write a code
|
|
_writeCode(f, &stat, (uint32_t)curCode, codeSize);
|
|
|
|
// insert the new run into the dictionary
|
|
codetree[curCode].m_next[nextValue] = (uint16_t)++maxCode;
|
|
|
|
if (maxCode >= (1ul << codeSize)) {
|
|
// dictionary entry count has broken a size barrier,
|
|
// we need more bits for codes
|
|
codeSize++;
|
|
}
|
|
if (maxCode == 4095) {
|
|
// the dictionary is full, clear it out and begin anew
|
|
_writeCode(f, &stat, clearCode, codeSize); // clear tree
|
|
|
|
memset(codetree, 0, sizeof(GifLzwNode)*4096);
|
|
codeSize = (uint32_t)(minCodeSize + 1);
|
|
maxCode = clearCode+1;
|
|
}
|
|
|
|
curCode = nextValue;
|
|
}
|
|
}
|
|
}
|
|
|
|
// compression footer
|
|
_writeCode(f, &stat, (uint32_t)curCode, codeSize);
|
|
_writeCode(f, &stat, clearCode, codeSize);
|
|
_writeCode(f, &stat, clearCode + 1, (uint32_t)minCodeSize + 1);
|
|
|
|
// write out the last partial chunk
|
|
while (stat.bitIndex) _writeBit(&stat, 0);
|
|
if (stat.chunkIndex) _writeChunk(f, &stat);
|
|
|
|
fputc(0, f); // image block terminator
|
|
|
|
free(codetree);
|
|
}
|
|
|
|
|
|
/************************************************************************/
|
|
/* External Class Implementation */
|
|
/************************************************************************/
|
|
|
|
|
|
bool gifBegin(GifWriter* writer, const char* filename, uint32_t width, uint32_t height, uint32_t delay)
|
|
{
|
|
#if defined(_MSC_VER) && (_MSC_VER >= 1400)
|
|
writer->f = 0;
|
|
fopen_s(&writer->f, filename, "wb");
|
|
#else
|
|
writer->f = fopen(filename, "wb");
|
|
#endif
|
|
if (!writer->f) return false;
|
|
|
|
writer->firstFrame = true;
|
|
|
|
// allocate
|
|
writer->oldImage = (uint8_t*)malloc(width*height*4);
|
|
writer->tmpImage = (uint8_t*)malloc(width*height*4);
|
|
|
|
fputs("GIF89a", writer->f);
|
|
|
|
// screen descriptor
|
|
fputc(width & 0xff, writer->f);
|
|
fputc((width >> 8) & 0xff, writer->f);
|
|
fputc(height & 0xff, writer->f);
|
|
fputc((height >> 8) & 0xff, writer->f);
|
|
|
|
fputc(0xf0, writer->f); // there is an unsorted global color table of 2 entries
|
|
fputc(0, writer->f); // background color
|
|
fputc(0, writer->f); // pixels are square (we need to specify this because it's 1989)
|
|
|
|
// now the "global" palette (really just a dummy palette)
|
|
// color 0: black
|
|
fputc(0, writer->f);
|
|
fputc(0, writer->f);
|
|
fputc(0, writer->f);
|
|
// color 1: also black
|
|
fputc(0, writer->f);
|
|
fputc(0, writer->f);
|
|
fputc(0, writer->f);
|
|
|
|
if(delay != 0) {
|
|
// animation header
|
|
fputc(0x21, writer->f); // extension
|
|
fputc(0xff, writer->f); // application specific
|
|
fputc(11, writer->f); // length 11
|
|
fputs("NETSCAPE2.0", writer->f); // yes, really
|
|
fputc(3, writer->f); // 3 bytes of NETSCAPE2.0 data
|
|
|
|
fputc(1, writer->f); // JUST BECAUSE
|
|
fputc(0, writer->f); // loop infinitely (byte 0)
|
|
fputc(0, writer->f); // loop infinitely (byte 1)
|
|
|
|
fputc(0, writer->f); // block terminator
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
bool gifWriteFrame(GifWriter* writer, const uint8_t* image, uint32_t width, uint32_t height, uint32_t delay, bool transparent)
|
|
{
|
|
if (!writer->f) return false;
|
|
|
|
const uint8_t* oldImage = writer->firstFrame? NULL : writer->oldImage;
|
|
writer->firstFrame = false;
|
|
|
|
GifPalette pal;
|
|
_makePalette(writer, oldImage, image, width, height, 8, &pal, transparent);
|
|
|
|
_thresholdImage(oldImage, image, writer->oldImage, width, height, &pal, transparent);
|
|
|
|
_writeLzwImage(writer->f, writer->oldImage, 0, 0, width, height, delay, &pal, transparent);
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
bool gifEnd(GifWriter* writer)
|
|
{
|
|
if (!writer->f) return false;
|
|
|
|
fputc(0x3b, writer->f); // end of file
|
|
fclose(writer->f);
|
|
free(writer->oldImage);
|
|
free(writer->tmpImage);
|
|
|
|
writer->f = NULL;
|
|
writer->oldImage = NULL;
|
|
|
|
return true;
|
|
}
|