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Fix error decoding pico-8 GIFs (fix aseprite#3922)
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@Gasparoken
Gasparoken committed Jul 18, 2023
1 parent 98366d3 commit a89e446
Showing 1 changed file with 131 additions and 147 deletions.
278 changes: 131 additions & 147 deletions src/app/file/gif_format.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -371,7 +371,7 @@ class GifDecoder {
}

// Merge this frame colors with the current palette
if (frameImage)
if (frameImage && m_sprite->palette(m_frameNum)->size() <= 256)
updatePalette(frameImage.get());

// Convert the sprite to RGB if we have more than 256 colors
Expand Down Expand Up @@ -492,177 +492,160 @@ class GifDecoder {
return colormap;
}

// Adds colors used in the GIF frame so we can draw it over
// m_currentImage. If the frame contains a local colormap, we try to
// find them in the current sprite palette (using
// Palette::findExactMatch()) so we don't add duplicated entries.
// To do so we use a Remap (m_remap variable) which matches the
// original GIF frame colors with the current sprite colors.
// Accumulates colors to get the final palette in the sprite.
// If the GIF file contains a global palette and no local palette
// on frame 0, we'll take the global palette as base,
// no matter if its colors are used or not in the image,
// then the new colors are used in each frame will be accumulated.
// If there is no global palette, the colors will accumulate
// as they are used in each frame.
// Note that the order of colors in the resulting palette will be
// very different from the order of the local palette of the
// corresponding GIF, since the unused colors will be discarded.
void updatePalette(const Image* frameImage) {
ColorMapObject* colormap = getFrameColormap();
const int ncolors = colormap->ColorCount;
int ncolors = colormap->ColorCount;
bool isLocalColormap = (m_gifFile->Image.ColorMap ? true: false);

GIF_TRACE("GIF: Local colormap=%d, ncolors=%d\n", isLocalColormap, ncolors);

// We'll calculate the list of used colormap indexes in this
// frameImage.
PalettePicks usedEntries(ncolors);
if (isLocalColormap) {
// With this we avoid discarding the transparent index when a
// frame indicates that it uses a specific index as transparent
// but the image is completely opaque anyway.
if (!m_opaque && m_frameNum == 0 && m_localTransparentIndex >= 0 &&
m_localTransparentIndex < ncolors) {
usedEntries[m_localTransparentIndex] = true;
}
// This holds the eventual necessity of increment in one color
// the palette and usedEntries in case of m_localTransparentIndex
// is out of bounds and non opaque sprite.
int extraEntry = 0;

if (m_frameNum == 0 && !isLocalColormap)
// Mark all entries as used if the colormap is global.
usedEntries.all();
else {
for (const auto& i : LockImageBits<IndexedTraits>(frameImage)) {
if (i >= 0 && i < ncolors && i != m_localTransparentIndex)
if (i >= 0 && i < ncolors) {
usedEntries[i] = true;
}
}
// GIF Case: unnamed.gif. If a pixel is equal to
// m_localtransparentindex in a frame > 0 in a sprite
// defined as opaque, it will be the same as leaving
// the m_bgindex color in said pixel.
// That's why we mark m_localTransparentIndex entry as not used.
if (m_opaque &&
0 <= m_localTransparentIndex &&
m_localTransparentIndex < usedEntries.size() &&
m_frameNum > 0) {
usedEntries[m_localTransparentIndex] = false;
}
// A sprite with transparent layer always needs a defined transparent
// entry to be able to represent transparent color.
// If the GIF is identified as a transparent sprite, we'll be forced
// to adopt a transparent entry (no matter if the sprite will end
// with all opaque pixels).
// That's why we must force m_localTransparentIndex as used entry.
if (m_frameNum == 0 && !m_opaque) {
// Regular case
if (0 <= m_localTransparentIndex &&
m_localTransparentIndex < ncolors)
usedEntries[m_localTransparentIndex] = true;
// Out of bounds case (will need an extra palette entry)
else if (m_localTransparentIndex >= ncolors)
extraEntry = 1;
}
}
// Mark all entries as used if the colormap is global.
else {
usedEntries.all();
}

// Number of colors (indexes) used in the frame image.
int usedNColors = usedEntries.picks();

// Check if we need an extra color equal to the bg color in a
// transparent frameImage.
bool needsExtraBgColor = false;
bool needCheckLocalTransparent = m_bgIndex != m_localTransparentIndex ||
(ncolors > m_localTransparentIndex
&& m_localTransparentIndex >= 0
&& usedEntries[m_localTransparentIndex]);

if (m_sprite->pixelFormat() == IMAGE_INDEXED &&
!m_opaque &&
needCheckLocalTransparent) {
for (const auto& i : LockImageBits<IndexedTraits>(frameImage)) {
if (i == m_bgIndex) {
needsExtraBgColor = true;
break;
const int usedNColors = usedEntries.picks();

resetRemap(256);

std::unique_ptr<Palette> palette;
if (m_frameNum == 0) {
palette = std::make_unique<Palette>(m_frameNum, usedNColors + extraEntry);
if (palette->size() > 256)
return;
// The final palette will have a "transparent index".
// That index will be stored in m_bgIndex.
// So we'll update the m_bgIndex only if the
// GIF is defined as transparent and the m_localTransparentIndex
// is a valid index on frame 0.
// If the GIF is defined as 'opaque' (i.e. no transparent color)
// m_bgIndex will be defined on GifDecoder constructor equal to
// SBackGroundColor or 0.
if (!m_opaque) {
// Regular case
if (0 <= m_localTransparentIndex &&
m_localTransparentIndex < ncolors)
m_bgIndex = m_localTransparentIndex;
// Out of bound case
else if (m_localTransparentIndex >= ncolors) {
m_bgIndex = palette->size() - 1;
m_remap.map(m_localTransparentIndex, m_bgIndex);
}
else
ASSERT(false); // Can it happen?
clear_image(m_currentImage.get(), m_bgIndex);
clear_image(m_previousImage.get(), m_bgIndex);
}
m_currentImage.get()->setMaskColor(m_bgIndex);
m_previousImage.get()->setMaskColor(m_bgIndex);
m_sprite->setTransparentColor(m_bgIndex);
}

std::unique_ptr<Palette> palette;
if (m_frameNum == 0)
palette.reset(new Palette(m_frameNum, usedNColors + (needsExtraBgColor ? 1: 0)));
else {
palette.reset(new Palette(*m_sprite->palette(m_frameNum-1)));
palette->setFrame(m_frameNum);
}
resetRemap(std::max(ncolors, palette->size()));

// Number of colors in the colormap that are part of the current
// sprite palette.
int found = 0;
if (m_frameNum > 0) {
ColorMapObject* globalCMap = m_gifFile->SColorMap;
ColorMapObject* localCMap = m_gifFile->Image.ColorMap;
if (globalCMap && !m_hasLocalColormaps)
found = usedEntries.size();
else {
for (int i=0; i<ncolors; ++i) {
if (!usedEntries[i])
continue;

if (localCMap && i < localCMap->ColorCount &&
rgba(localCMap->Colors[i].Red,
localCMap->Colors[i].Green,
localCMap->Colors[i].Blue, 255) == palette->getEntry(i)) {
++found;
continue;
}

int j = palette->findExactMatch(colormap->Colors[i].Red,
colormap->Colors[i].Green,
colormap->Colors[i].Blue, 255,
(m_opaque ? -1: m_bgIndex));
if (j >= 0) {
m_remap.map(i, j);
++found;
}
}
}
}

// All needed colors in the colormap are present in the current
// palette.
if (found == usedNColors)
return;

// In other case, we need to add the missing colors...

// First index that acts like a base for new colors in palette.
int base = (m_frameNum == 0 ? 0: palette->size());

// Number of colors in the image that aren't in the palette.
int missing = (usedNColors - found);

GIF_TRACE("GIF: Bg index=%d,\n"
" Local transparent index=%d,\n"
" Need extra index to show bg color=%d,\n "
" Found colors in palette=%d,\n"
" Used colors in local pixels=%d,\n"
" Base for new colors in palette=%d,\n"
" Colors in the image missing in the palette=%d,\n"
" New palette size=%d\n",
m_bgIndex, m_localTransparentIndex, needsExtraBgColor,
found, usedNColors, base, missing,
base + missing + (needsExtraBgColor ? 1: 0));

Palette oldPalette(*palette);
palette->resize(base + missing + (needsExtraBgColor ? 1: 0));
resetRemap(std::max(ncolors, palette->size()));

for (int i=0; i<ncolors; ++i) {
if (!usedEntries[i])
continue;

int j = -1;

if (m_frameNum > 0) {
j = oldPalette.findExactMatch(
colormap->Colors[i].Red,
colormap->Colors[i].Green,
colormap->Colors[i].Blue, 255,
(m_opaque ? -1: m_bgIndex));
}

if (j < 0) {
j = base++;
// On frame 0 fill the palette with used colors and remap
if (m_frameNum == 0) {
int j = 0;
for (int i = 0; i < ncolors; i++) {
if (!usedEntries[i])
continue;
palette->setEntry(j, colormap2rgba(colormap, i));
m_remap.map(i, j);
j++;
}
m_remap.map(i, j);
}
// Frames > 0, find new colors on the palette and remap or
// add new used color and remap.
else {
for (int i=0; i<ncolors; ++i) {

if (!usedEntries[i])
continue;

// If by chance, the actual used entry 'i'
// matches with the palette entry 'i', it isn't
// need to find a match or add a new color to the palette.
if (i < palette->size() &&
(i != m_bgIndex || m_opaque) &&
colormap &&
i < colormap->ColorCount &&
rgba(colormap->Colors[i].Red,
colormap->Colors[i].Green,
colormap->Colors[i].Blue,
255) == palette->getEntry(i)) {
continue;
}

if (needsExtraBgColor) {
int i = m_bgIndex;
int j = base++;
palette->setEntry(j, colormap2rgba(colormap, i));
// m_firstLocalColorMap, is used only if we have no global color map in the gif source,
// and we want to preserve original color indexes, as much we can.
// If the palette size is > 256, m_firstLocalColormal is no more useful, because
// the sprite pixel format will be converted in RGBA image, and the colors will
// be picked from the sprite palette, instead of m_firstLocalColorMap.
if (m_firstLocalColormap && m_firstLocalColormap->ColorCount > j) {
// We need add this extra color to m_firstLocalColormap, because
// it might has not been considered in the first getFrameColormap execution.
// (this happen when: in the first execution of getFrameColormap function
// an extra color was not needed)
m_firstLocalColormap->Colors[j].Red = rgba_getr(palette->getEntry(j));
m_firstLocalColormap->Colors[j].Green = rgba_getg(palette->getEntry(j));
m_firstLocalColormap->Colors[j].Blue = rgba_getb(palette->getEntry(j));
int j = palette->findExactMatch(
colormap->Colors[i].Red,
colormap->Colors[i].Green,
colormap->Colors[i].Blue, 255,
m_opaque ? -1: m_bgIndex);
if (j < 0) {
palette->resize(palette->size() + 1);
j = palette->size() - 1;
palette->setEntry(j, colormap2rgba(colormap, i));
}
// If the palette size is >256, we'll stop updating
// the palette for the remaining frames because
// we'll switch to RGB pixel format, so we have no interest
// in further managing or remapping colors in the palette.
if (j >= 256)
break;
m_remap.map(i, j);
}
m_remap.map(i, j);
}

ASSERT(base == palette->size());
m_sprite->setPalette(palette.get(), false);
}

Expand Down Expand Up @@ -818,7 +801,7 @@ class GifDecoder {
// INDEXED->RGB conversions
m_sprite->palette(cel->frame()),
m_opaque,
m_bgIndex,
0,
nullptr));

m_sprite->replaceImage(oldImage->id(), newImage);
Expand All @@ -831,7 +814,7 @@ class GifDecoder {
nullptr,
m_sprite->palette(m_frameNum),
m_opaque,
m_bgIndex));
0));

m_previousImage.reset(
render::convert_pixel_format
Expand All @@ -840,9 +823,10 @@ class GifDecoder {
nullptr,
m_sprite->palette(std::max(0, m_frameNum-1)),
m_opaque,
m_bgIndex));
0));

m_sprite->setPixelFormat(IMAGE_RGB);
m_sprite->setTransparentColor(0);
}

void remapToGlobalColormap(ColorMapObject* colormap) {
Expand Down

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