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saver/gif: code refactoring

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Remove unused dithering logics for reducing binary size.
This is not quite effective for vector images.
This commit is contained in:
Hermet Park 2023-11-15 11:31:25 +09:00 • committed by Hermet Park
parent 6e6dd8a97e
commit 3999762d3b
1 changed files with 9 additions and 164 deletions
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173
src/savers/gif/gif.h
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@ -205,7 +205,7 @@ void GifPartitionByMedian(uint8_t* image, int left, int right, int com, int need
}
// Builds a palette by creating a balanced k-d tree of all pixels in the image
void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, int splitElt, int splitDist, int treeNode, bool buildForDither, GifPalette* pal)
void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, int splitElt, int splitDist, int treeNode, GifPalette* pal)
{
if(lastElt <= firstElt || numPixels == 0)
return;
@ -213,48 +213,6 @@ void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, i
// base case, bottom of the tree
if(lastElt == firstElt+1)
{
if(buildForDither)
{
// Dithering needs at least one color as dark as anything
// in the image and at least one brightest color -
// otherwise it builds up error and produces strange artifacts
if( firstElt == 1 )
{
// special case: the darkest color in the image
uint32_t r=255, g=255, b=255;
for(int ii=0; ii<numPixels; ++ii)
{
r = (uint32_t)GifIMin((int32_t)r, image[ii * 4 + 0]);
g = (uint32_t)GifIMin((int32_t)g, image[ii * 4 + 1]);
b = (uint32_t)GifIMin((int32_t)b, image[ii * 4 + 2]);
}
pal->r[firstElt] = (uint8_t)r;
pal->g[firstElt] = (uint8_t)g;
pal->b[firstElt] = (uint8_t)b;
return;
}
if( firstElt == (1 << pal->bitDepth)-1 )
{
// special case: the lightest color in the image
uint32_t r=0, g=0, b=0;
for(int ii=0; ii<numPixels; ++ii)
{
r = (uint32_t)GifIMax((int32_t)r, image[ii * 4 + 0]);
g = (uint32_t)GifIMax((int32_t)g, image[ii * 4 + 1]);
b = (uint32_t)GifIMax((int32_t)b, image[ii * 4 + 2]);
}
pal->r[firstElt] = (uint8_t)r;
pal->g[firstElt] = (uint8_t)g;
pal->b[firstElt] = (uint8_t)b;
return;
}
}
// otherwise, take the average of all colors in this subcube
uint64_t r=0, g=0, b=0;
for(int ii=0; ii<numPixels; ++ii)
@ -316,8 +274,8 @@ void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, i
pal->treeSplitElt[treeNode] = (uint8_t)splitCom;
pal->treeSplit[treeNode] = image[subPixelsA*4+splitCom];
GifSplitPalette(image, subPixelsA, firstElt, splitElt, splitElt-splitDist, splitDist/2, treeNode*2, buildForDither, pal);
GifSplitPalette(image+subPixelsA*4, subPixelsB, splitElt, lastElt, splitElt+splitDist, splitDist/2, treeNode*2+1, buildForDither, pal);
GifSplitPalette(image, subPixelsA, firstElt, splitElt, splitElt-splitDist, splitDist/2, treeNode*2, pal);
GifSplitPalette(image+subPixelsA*4, subPixelsB, splitElt, lastElt, splitElt+splitDist, splitDist/2, treeNode*2+1, pal);
}
// Finds all pixels that have changed from the previous image and
@ -350,7 +308,7 @@ int GifPickChangedPixels( const uint8_t* lastFrame, uint8_t* frame, int numPixel
// Creates a palette by placing all the image pixels in a k-d tree and then averaging the blocks at the bottom.
// This is known as the "modified median split" technique
void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_t width, uint32_t height, int bitDepth, bool buildForDither, GifPalette* pPal )
void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_t width, uint32_t height, int bitDepth, GifPalette* pPal )
{
pPal->bitDepth = bitDepth;
@ -368,7 +326,7 @@ void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_
const int splitElt = lastElt/2;
const int splitDist = splitElt/2;
GifSplitPalette(destroyableImage, numPixels, 1, lastElt, splitElt, splitDist, 1, buildForDither, pPal);
GifSplitPalette(destroyableImage, numPixels, 1, lastElt, splitElt, splitDist, 1, pPal);
GIF_TEMP_FREE(destroyableImage);
@ -379,115 +337,6 @@ void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_
pPal->r[0] = pPal->g[0] = pPal->b[0] = 0;
}
// Implements Floyd-Steinberg dithering, writes palette value to alpha
void GifDitherImage( const uint8_t* lastFrame, const uint8_t* nextFrame, uint8_t* outFrame, uint32_t width, uint32_t height, GifPalette* pPal )
{
int numPixels = (int)(width * height);
// quantPixels initially holds color*256 for all pixels
// The extra 8 bits of precision allow for sub-single-color error values
// to be propagated
int32_t *quantPixels = (int32_t *)GIF_TEMP_MALLOC(sizeof(int32_t) * (size_t)numPixels * 4);
for( int ii=0; ii<numPixels*4; ++ii )
{
uint8_t pix = nextFrame[ii];
int32_t pix16 = (int32_t)(pix) * 256;
quantPixels[ii] = pix16;
}
for( uint32_t yy=0; yy<height; ++yy )
{
for( uint32_t xx=0; xx<width; ++xx )
{
int32_t* nextPix = quantPixels + 4*(yy*width+xx);
const uint8_t* lastPix = lastFrame? lastFrame + 4*(yy*width+xx) : NULL;
// Compute the colors we want (rounding to nearest)
int32_t rr = (nextPix[0] + 127) / 256;
int32_t gg = (nextPix[1] + 127) / 256;
int32_t bb = (nextPix[2] + 127) / 256;
// if it happens that we want the color from last frame, then just write out
// a transparent pixel
if( lastFrame &&
lastPix[0] == rr &&
lastPix[1] == gg &&
lastPix[2] == bb )
{
nextPix[0] = rr;
nextPix[1] = gg;
nextPix[2] = bb;
nextPix[3] = kGifTransIndex;
continue;
}
int32_t bestDiff = 1000000;
int32_t bestInd = kGifTransIndex;
// Search the palete
GifGetClosestPaletteColor(pPal, rr, gg, bb, &bestInd, &bestDiff, 1);
// Write the result to the temp buffer
int32_t r_err = nextPix[0] - (int32_t)(pPal->r[bestInd]) * 256;
int32_t g_err = nextPix[1] - (int32_t)(pPal->g[bestInd]) * 256;
int32_t b_err = nextPix[2] - (int32_t)(pPal->b[bestInd]) * 256;
nextPix[0] = pPal->r[bestInd];
nextPix[1] = pPal->g[bestInd];
nextPix[2] = pPal->b[bestInd];
nextPix[3] = bestInd;
// Propagate the error to the four adjacent locations
// that we haven't touched yet
int quantloc_7 = (int)(yy * width + xx + 1);
int quantloc_3 = (int)(yy * width + width + xx - 1);
int quantloc_5 = (int)(yy * width + width + xx);
int quantloc_1 = (int)(yy * width + width + xx + 1);
if(quantloc_7 < numPixels)
{
int32_t* pix7 = quantPixels+4*quantloc_7;
pix7[0] += GifIMax( -pix7[0], r_err * 7 / 16 );
pix7[1] += GifIMax( -pix7[1], g_err * 7 / 16 );
pix7[2] += GifIMax( -pix7[2], b_err * 7 / 16 );
}
if(quantloc_3 < numPixels)
{
int32_t* pix3 = quantPixels+4*quantloc_3;
pix3[0] += GifIMax( -pix3[0], r_err * 3 / 16 );
pix3[1] += GifIMax( -pix3[1], g_err * 3 / 16 );
pix3[2] += GifIMax( -pix3[2], b_err * 3 / 16 );
}
if(quantloc_5 < numPixels)
{
int32_t* pix5 = quantPixels+4*quantloc_5;
pix5[0] += GifIMax( -pix5[0], r_err * 5 / 16 );
pix5[1] += GifIMax( -pix5[1], g_err * 5 / 16 );
pix5[2] += GifIMax( -pix5[2], b_err * 5 / 16 );
}
if(quantloc_1 < numPixels)
{
int32_t* pix1 = quantPixels+4*quantloc_1;
pix1[0] += GifIMax( -pix1[0], r_err / 16 );
pix1[1] += GifIMax( -pix1[1], g_err / 16 );
pix1[2] += GifIMax( -pix1[2], b_err / 16 );
}
}
}
// Copy the palettized result to the output buffer
for( int ii=0; ii<numPixels*4; ++ii )
{
outFrame[ii] = (uint8_t)quantPixels[ii];
}
GIF_TEMP_FREE(quantPixels);
}
// Picks palette colors for the image using simple thresholding, no dithering
void GifThresholdImage( const uint8_t* lastFrame, const uint8_t* nextFrame, uint8_t* outFrame, uint32_t width, uint32_t height, GifPalette* pPal )
{
@ -735,9 +584,8 @@ typedef struct
// Creates a gif file.
// The input GIFWriter is assumed to be uninitialized.
// The delay value is the time between frames in hundredths of a second - note that not all viewers pay much attention to this value.
bool GifBegin( GifWriter* writer, const char* filename, uint32_t width, uint32_t height, uint32_t delay, int32_t bitDepth = 8, bool dither = false )
bool GifBegin( GifWriter* writer, const char* filename, uint32_t width, uint32_t height, uint32_t delay)
{
(void)bitDepth; (void)dither; // Mute "Unused argument" warnings
#if defined(_MSC_VER) && (_MSC_VER >= 1400)
writer->f = 0;
fopen_s(&writer->f, filename, "wb");
@ -796,7 +644,7 @@ bool GifBegin( GifWriter* writer, const char* filename, uint32_t width, uint32_t
// The GIFWriter should have been created by GIFBegin.
// AFAIK, it is legal to use different bit depths for different frames of an image -
// this may be handy to save bits in animations that don't change much.
bool GifWriteFrame( GifWriter* writer, const uint8_t* image, uint32_t width, uint32_t height, uint32_t delay, int bitDepth = 8, bool dither = false )
bool GifWriteFrame(GifWriter* writer, const uint8_t* image, uint32_t width, uint32_t height, uint32_t delay, int bitDepth = 8)
{
if(!writer->f) return false;
@ -804,12 +652,9 @@ bool GifWriteFrame( GifWriter* writer, const uint8_t* image, uint32_t width, uin
writer->firstFrame = false;
GifPalette pal;
GifMakePalette((dither? NULL : oldImage), image, width, height, bitDepth, dither, &pal);
GifMakePalette(oldImage, image, width, height, bitDepth, &pal);
if(dither)
GifDitherImage(oldImage, image, writer->oldImage, width, height, &pal);
else
GifThresholdImage(oldImage, image, writer->oldImage, width, height, &pal);
GifThresholdImage(oldImage, image, writer->oldImage, width, height, &pal);
GifWriteLzwImage(writer->f, writer->oldImage, 0, 0, width, height, delay, &pal);