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thorvg/src/loaders/lottie/tvgLottieModifier.cpp
Mira Grudzinska 27e78095ff lottie: fix offset with miter join 
One point was skipped during the creation of the offset
corner. The error was not visible because the point lies
on the line, but it will become apparent if further
modifiers are applied to the object (not supported now).
2025-06-13 11:36:22 +09:00

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/*
* Copyright (c) 2024 - 2025 the ThorVG project. All rights reserved.
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "tvgLottieModifier.h"
/************************************************************************/
/* Internal Class Implementation */
/************************************************************************/
static bool _colinear(const Point* p)
{
return tvg::zero(*p - *(p + 1)) && tvg::zero(*(p + 2) - *(p + 3));
}
static void _roundCorner(Array<PathCommand>& cmds, Array<Point>& pts, Point& prev, Point& curr, Point& next, float r)
{
auto lenPrev = length(prev - curr);
auto rPrev = lenPrev > 0.0f ? 0.5f * std::min(lenPrev * 0.5f, r) / lenPrev : 0.0f;
auto lenNext = length(next - curr);
auto rNext = lenNext > 0.0f ? 0.5f * std::min(lenNext * 0.5f, r) / lenNext : 0.0f;
auto dPrev = rPrev * (curr - prev);
auto dNext = rNext * (curr - next);
pts.push(curr - 2.0f * dPrev);
pts.push(curr - dPrev);
pts.push(curr - dNext);
pts.push(curr - 2.0f * dNext);
cmds.push(PathCommand::LineTo);
cmds.push(PathCommand::CubicTo);
}
static bool _zero(Point& p1, Point& p2)
{
constexpr float epsilon = 1e-3f;
return fabsf(p1.x / p2.x - 1.0f) < epsilon && fabsf(p1.y / p2.y - 1.0f) < epsilon;
}
static bool _intersect(Line& line1, Line& line2, Point& intersection, bool& inside)
{
if (_zero(line1.pt2, line2.pt1)) {
intersection = line1.pt2;
inside = true;
return true;
}
constexpr float epsilon = 1e-3f;
float denom = (line1.pt2.x - line1.pt1.x) * (line2.pt2.y - line2.pt1.y) - (line1.pt2.y - line1.pt1.y) * (line2.pt2.x - line2.pt1.x);
if (fabsf(denom) < epsilon) return false;
float t = ((line2.pt1.x - line1.pt1.x) * (line2.pt2.y - line2.pt1.y) - (line2.pt1.y - line1.pt1.y) * (line2.pt2.x - line2.pt1.x)) / denom;
float u = ((line2.pt1.x - line1.pt1.x) * (line1.pt2.y - line1.pt1.y) - (line2.pt1.y - line1.pt1.y) * (line1.pt2.x - line1.pt1.x)) / denom;
intersection.x = line1.pt1.x + t * (line1.pt2.x - line1.pt1.x);
intersection.y = line1.pt1.y + t * (line1.pt2.y - line1.pt1.y);
inside = t >= -epsilon && t <= 1.0f + epsilon && u >= -epsilon && u <= 1.0f + epsilon;
return true;
}
static Line _offset(Point& p1, Point& p2, float offset)
{
auto scaledNormal = normal(p1, p2) * offset;
return {p1 + scaledNormal, p2 + scaledNormal};
}
static bool _clockwise(Point* pts, uint32_t n)
{
auto area = 0.0f;
for (uint32_t i = 0; i < n - 1; i++) {
area += cross(pts[i], pts[i + 1]);
}
area += cross(pts[n - 1], pts[0]);;
return area < 0.0f;
}
void LottieOffsetModifier::corner(RenderPath& out, Line& line, Line& nextLine, uint32_t movetoOutIndex, bool nextClose)
{
bool inside{};
Point intersect{};
if (_intersect(line, nextLine, intersect, inside)) {
if (inside) {
if (nextClose) out.pts[movetoOutIndex] = intersect;
out.pts.push(intersect);
} else {
out.pts.push(line.pt2);
if (join == StrokeJoin::Round) {
out.cmds.push(PathCommand::CubicTo);
out.pts.push((line.pt2 + intersect) * 0.5f);
out.pts.push((nextLine.pt1 + intersect) * 0.5f);
out.pts.push(nextLine.pt1);
} else if (join == StrokeJoin::Miter) {
auto norm = normal(line.pt1, line.pt2);
auto nextNorm = normal(nextLine.pt1, nextLine.pt2);
auto miterDirection = (norm + nextNorm) / length(norm + nextNorm);
if (1.0f <= miterLimit * fabsf(miterDirection.x * norm.x + miterDirection.y * norm.y)) {
out.cmds.push(PathCommand::LineTo);
out.pts.push(intersect);
}
out.cmds.push(PathCommand::LineTo);
out.pts.push(nextLine.pt1);
} else {
out.cmds.push(PathCommand::LineTo);
out.pts.push(nextLine.pt1);
}
}
} else out.pts.push(line.pt2);
}
void LottieOffsetModifier::line(RenderPath& out, PathCommand* inCmds, uint32_t inCmdsCnt, Point* inPts, uint32_t& curPt, uint32_t curCmd, State& state, float offset, bool degenerated)
{
if (tvg::zero(inPts[curPt - 1] - inPts[curPt])) {
++curPt;
return;
}
if (inCmds[curCmd - 1] != PathCommand::LineTo) state.line = _offset(inPts[curPt - 1], inPts[curPt], offset);
if (state.moveto) {
out.cmds.push(PathCommand::MoveTo);
state.movetoOutIndex = out.pts.count;
out.pts.push(state.line.pt1);
state.firstLine = state.line;
state.moveto = false;
}
auto nonDegeneratedCubic = [&](uint32_t cmd, uint32_t pt) {
return inCmds[cmd] == PathCommand::CubicTo && !tvg::zero(inPts[pt] - inPts[pt + 1]) && !tvg::zero(inPts[pt + 2] - inPts[pt + 3]);
};
out.cmds.push(PathCommand::LineTo);
if (curCmd + 1 == inCmdsCnt || inCmds[curCmd + 1] == PathCommand::MoveTo || nonDegeneratedCubic(curCmd + 1, curPt + degenerated)) {
out.pts.push(state.line.pt2);
++curPt;
return;
}
Line nextLine = state.firstLine;
if (inCmds[curCmd + 1] == PathCommand::LineTo) nextLine = _offset(inPts[curPt + degenerated], inPts[curPt + 1 + degenerated], offset);
else if (inCmds[curCmd + 1] == PathCommand::CubicTo) nextLine = _offset(inPts[curPt + 1 + degenerated], inPts[curPt + 2 + degenerated], offset);
else if (inCmds[curCmd + 1] == PathCommand::Close && !_zero(inPts[curPt + degenerated], inPts[state.movetoInIndex + degenerated]))
nextLine = _offset(inPts[curPt + degenerated], inPts[state.movetoInIndex + degenerated], offset);
corner(out, state.line, nextLine, state.movetoOutIndex, inCmds[curCmd + 1] == PathCommand::Close);
state.line = nextLine;
++curPt;
}
/************************************************************************/
/* External Class Implementation */
/************************************************************************/
bool LottieRoundnessModifier::modifyPath(PathCommand* inCmds, uint32_t inCmdsCnt, Point* inPts, uint32_t inPtsCnt, Matrix* transform, RenderPath& out)
{
buffer->clear();
auto& path = (next) ? *buffer : out;
path.cmds.reserve(inCmdsCnt * 2);
path.pts.reserve((uint32_t)(inPtsCnt * 1.5));
auto pivot = path.pts.count;
uint32_t startIndex = 0;
for (uint32_t iCmds = 0, iPts = 0; iCmds < inCmdsCnt; ++iCmds) {
switch (inCmds[iCmds]) {
case PathCommand::MoveTo: {
startIndex = path.pts.count;
path.cmds.push(PathCommand::MoveTo);
path.pts.push(inPts[iPts++]);
break;
}
case PathCommand::CubicTo: {
if (iCmds < inCmdsCnt - 1 && _colinear(inPts + iPts - 1)) {
auto& prev = inPts[iPts - 1];
auto& curr = inPts[iPts + 2];
if (inCmds[iCmds + 1] == PathCommand::CubicTo && _colinear(inPts + iPts + 2)) {
_roundCorner(path.cmds, path.pts, prev, curr, inPts[iPts + 5], r);
iPts += 3;
break;
} else if (inCmds[iCmds + 1] == PathCommand::Close) {
_roundCorner(path.cmds, path.pts, prev, curr, inPts[2], r);
path.pts[startIndex] = path.pts.last();
iPts += 3;
break;
}
}
path.cmds.push(PathCommand::CubicTo);
path.pts.push(inPts[iPts++]);
path.pts.push(inPts[iPts++]);
path.pts.push(inPts[iPts++]);
break;
}
case PathCommand::Close: {
path.cmds.push(PathCommand::Close);
break;
}
default: break;
}
}
if (transform) {
for (auto i = pivot; i < path.pts.count; ++i) {
path.pts[i] *= *transform;
}
}
if (next) return next->modifyPath(path.cmds.data, path.cmds.count, path.pts.data, path.pts.count, transform, out);
return true;
}
bool LottieRoundnessModifier::modifyPolystar(RenderPath& in, RenderPath& out, float outerRoundness, bool hasRoundness)
{
constexpr auto ROUNDED_POLYSTAR_MAGIC_NUMBER = 0.47829f;
buffer->clear();
auto& path = (next) ? *buffer : out;
auto len = length(in.pts[1] - in.pts[2]);
auto r = len > 0.0f ? ROUNDED_POLYSTAR_MAGIC_NUMBER * std::min(len * 0.5f, this->r) / len : 0.0f;
if (hasRoundness) {
path.cmds.grow((uint32_t)(1.5 * in.cmds.count));
path.pts.grow((uint32_t)(4.5 * in.cmds.count));
int start = 3 * tvg::zero(outerRoundness);
path.cmds.push(PathCommand::MoveTo);
path.pts.push(in.pts[start]);
for (uint32_t i = 1 + start; i < in.pts.count; i += 6) {
auto& prev = in.pts[i];
auto& curr = in.pts[i + 2];
auto& next = (i < in.pts.count - start) ? in.pts[i + 4] : in.pts[2];
auto& nextCtrl = (i < in.pts.count - start) ? in.pts[i + 5] : in.pts[3];
auto dNext = r * (curr - next);
auto dPrev = r * (curr - prev);
auto p0 = curr - 2.0f * dPrev;
auto p1 = curr - dPrev;
auto p2 = curr - dNext;
auto p3 = curr - 2.0f * dNext;
path.cmds.push(PathCommand::CubicTo);
path.pts.push(prev); path.pts.push(p0); path.pts.push(p0);
path.cmds.push(PathCommand::CubicTo);
path.pts.push(p1); path.pts.push(p2); path.pts.push(p3);
path.cmds.push(PathCommand::CubicTo);
path.pts.push(p3); path.pts.push(next); path.pts.push(nextCtrl);
}
} else {
path.cmds.grow(2 * in.cmds.count);
path.pts.grow(4 * in.cmds.count);
auto dPrev = r * (in.pts[1] - in.pts[0]);
auto p = in.pts[0] + 2.0f * dPrev;
path.cmds.push(PathCommand::MoveTo);
path.pts.push(p);
for (uint32_t i = 1; i < in.pts.count; ++i) {
auto& curr = in.pts[i];
auto& next = (i == in.pts.count - 1) ? in.pts[1] : in.pts[i + 1];
auto dNext = r * (curr - next);
auto p0 = curr - 2.0f * dPrev;
auto p1 = curr - dPrev;
auto p2 = curr - dNext;
auto p3 = curr - 2.0f * dNext;
path.cmds.push(PathCommand::LineTo);
path.pts.push(p0);
path.cmds.push(PathCommand::CubicTo);
path.pts.push(p1); path.pts.push(p2); path.pts.push(p3);
dPrev = -1.0f * dNext;
}
}
path.cmds.push(PathCommand::Close);
if (next) return next->modifyPolystar(path, out, outerRoundness, hasRoundness);
return true;
}
bool LottieRoundnessModifier::modifyRect(Point& size, float& r)
{
r = std::min(this->r, std::max(size.x, size.y) * 0.5f);
return true;
}
bool LottieOffsetModifier::modifyPath(PathCommand* inCmds, uint32_t inCmdsCnt, Point* inPts, uint32_t inPtsCnt, TVG_UNUSED Matrix* transform, RenderPath& out)
{
if (next) TVGERR("LOTTIE", "Offset has a next modifier?");
out.cmds.reserve(inCmdsCnt * 2);
out.pts.reserve(inPtsCnt * (join == StrokeJoin::Round ? 4 : 2));
Array<Bezier> stack{5};
State state;
auto offset = _clockwise(inPts, inPtsCnt) ? this->offset : -this->offset;
auto threshold = 1.0f / fabsf(offset) + 1.0f;
for (uint32_t iCmd = 0, iPt = 0; iCmd < inCmdsCnt; ++iCmd) {
if (inCmds[iCmd] == PathCommand::MoveTo) {
state.moveto = true;
state.movetoInIndex = iPt++;
} else if (inCmds[iCmd] == PathCommand::LineTo) {
line(out, inCmds, inCmdsCnt, inPts, iPt, iCmd, state, offset, false);
} else if (inCmds[iCmd] == PathCommand::CubicTo) {
//cubic degenerated to a line
if (tvg::zero(inPts[iPt - 1] - inPts[iPt]) || tvg::zero(inPts[iPt + 1] - inPts[iPt + 2])) {
++iPt;
line(out, inCmds, inCmdsCnt, inPts, iPt, iCmd, state, offset, true);
++iPt;
continue;
}
stack.push({inPts[iPt - 1], inPts[iPt], inPts[iPt + 1], inPts[iPt + 2]});
while (!stack.empty()) {
auto& bezier = stack.last();
auto len = tvg::length(bezier.start - bezier.ctrl1) + tvg::length(bezier.ctrl1 - bezier.ctrl2) + tvg::length(bezier.ctrl2 - bezier.end);
if (len > threshold * bezier.length()) {
Bezier next;
bezier.split(0.5f, next);
stack.push(next);
continue;
}
stack.pop();
auto line1 = _offset(bezier.start, bezier.ctrl1, offset);
auto line2 = _offset(bezier.ctrl1, bezier.ctrl2, offset);
auto line3 = _offset(bezier.ctrl2, bezier.end, offset);
if (state.moveto) {
out.cmds.push(PathCommand::MoveTo);
state.movetoOutIndex = out.pts.count;
out.pts.push(line1.pt1);
state.firstLine = line1;
state.moveto = false;
}
bool inside{};
Point intersect{};
_intersect(line1, line2, intersect, inside);
out.pts.push(intersect);
_intersect(line2, line3, intersect, inside);
out.pts.push(intersect);
out.pts.push(line3.pt2);
out.cmds.push(PathCommand::CubicTo);
}
iPt += 3;
}
else {
if (!_zero(inPts[iPt - 1], inPts[state.movetoInIndex])) {
out.cmds.push(PathCommand::LineTo);
corner(out, state.line, state.firstLine, state.movetoOutIndex, true);
}
out.cmds.push(PathCommand::Close);
}
}
return true;
}
bool LottieOffsetModifier::modifyPolystar(RenderPath& in, RenderPath& out, TVG_UNUSED float, TVG_UNUSED bool)
{
return modifyPath(in.cmds.data, in.cmds.count, in.pts.data, in.pts.count, nullptr, out);
}
bool LottieOffsetModifier::modifyRect(RenderPath& in, RenderPath& out)
{
return modifyPath(in.cmds.data, in.cmds.count, in.pts.data, in.pts.count, nullptr, out);
}
bool LottieOffsetModifier::modifyEllipse(Point& radius)
{
radius.x += offset;
radius.y += offset;
return true;
}
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