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bug. Catch exceptions thrown by giflib #257

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Merged
remiolivier-discord merged 2 commits into from
Jun 11, 2025
Merged

bug. Catch exceptions thrown by giflib #257

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98cc39b
catch exception thrown from giflib
remiolivier-discord Jun 11, 2025
3977984
add gifdeleter
remiolivier-discord Jun 11, 2025
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98 changes: 73 additions & 25 deletions giflib.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -80,30 +80,78 @@ int decode_func(GifFileType* gif, GifByteType* buf, int len)
return read_len;
}

// Custom deleter for GIF files
struct GifFileDeleter {
void operator()(GifFileType* gif) {
if (gif) {
int error = 0;
DGifCloseFile(gif, &error);
}
}
};

/**
* Creates a GIF decoder from an OpenCV matrix.
*
* @param buf Pointer to an OpenCV matrix containing GIF data
* @return Pointer to the created decoder, or nullptr if creation fails
*
* Requirements:
* - buf must be a valid pointer to a cv::Mat
* - The matrix must contain valid GIF data
* - The GIF dimensions must be positive and not cause integer overflow
*/
giflib_decoder giflib_decoder_create(const opencv_mat buf)
{
giflib_decoder d = new struct giflib_decoder_struct();
memset(d, 0, sizeof(struct giflib_decoder_struct));
d->mat = static_cast<const cv::Mat*>(buf);
if (!buf) {
return nullptr;
}

std::unique_ptr<struct giflib_decoder_struct> d;
std::unique_ptr<GifFileType, GifFileDeleter> gif;
int error = 0;
GifFileType* gif = DGifOpen(d, decode_func, &error);

try {
d = std::make_unique<struct giflib_decoder_struct>();
} catch (const std::bad_alloc&) {
return nullptr;
}

try {
d->mat = static_cast<const cv::Mat*>(buf);
} catch (const std::bad_cast&) {
return nullptr;
}

gif.reset(DGifOpen(d.get(), decode_func, &error));
if (error) {
delete d;
return NULL;
return nullptr;
}
d->gif = gif.get();

if (d->gif->SWidth <= 0 || d->gif->SHeight <= 0) {
// Invalid dimensions
return nullptr;
}

// Check if the total size would overflow
if (d->gif->SHeight > SIZE_MAX / BYTES_PER_PIXEL ||
d->gif->SWidth > SIZE_MAX / (d->gif->SHeight * BYTES_PER_PIXEL)) {
return nullptr;
}
d->gif = gif;

// buffer for previous frame's content using vector (no need for explicit error checking)
try {
// buffer for previous frame's content using vector
d->prev_frame_bgra.resize(d->gif->SWidth * d->gif->SHeight * BYTES_PER_PIXEL);
} catch (const std::bad_alloc&) {
DGifCloseFile(gif, &error);
delete d;
return NULL;
return nullptr;
} catch (const std::length_error&) {
return nullptr;
}

return d;
// Release ownership of the GIF file to the decoder
gif.release();
return d.release();
}

int giflib_decoder_get_width(const giflib_decoder d)
Expand Down Expand Up @@ -399,7 +447,7 @@ static bool giflib_decoder_render_frame(giflib_decoder d, GraphicsControlBlock*
// 1. Negative offsets: adjust width/height and set offset to 0
// 2. Frames that extend beyond canvas: clip to canvas boundaries
// 3. Invalid dimensions: ensure width/height are non-negative

// Handle negative left offset
if (prev_frame_left < 0) {
prev_frame_width += prev_frame_left;
Expand Down Expand Up @@ -537,11 +585,11 @@ static void extract_background_color(GifFileType* gif,
uint8_t* a)
{
bool have_transparency = (gcb->TransparentColor != NO_TRANSPARENT_COLOR);

if (have_transparency) {
// For transparent GIFs, use background color with alpha=0 to preserve color information
if (gif->SColorMap && gif->SColorMap->Colors &&
gif->SBackGroundColor >= 0 &&
if (gif->SColorMap && gif->SColorMap->Colors &&
gif->SBackGroundColor >= 0 &&
gif->SBackGroundColor < gif->SColorMap->ColorCount) {
*r = gif->SColorMap->Colors[gif->SBackGroundColor].Red;
*g = gif->SColorMap->Colors[gif->SBackGroundColor].Green;
Expand All @@ -554,8 +602,8 @@ static void extract_background_color(GifFileType* gif,
}
*a = 0; // Always transparent if GCB has transparency
}
else if (gif->SColorMap && gif->SColorMap->Colors &&
gif->SBackGroundColor >= 0 &&
else if (gif->SColorMap && gif->SColorMap->Colors &&
gif->SBackGroundColor >= 0 &&
gif->SBackGroundColor < gif->SColorMap->ColorCount) {
// For non-transparent GIFs with valid background color, use opaque background
*r = gif->SColorMap->Colors[gif->SBackGroundColor].Red;
Expand Down Expand Up @@ -744,9 +792,9 @@ bool giflib_encoder_init(giflib_encoder e, const giflib_decoder d, int width, in
// preserve # of palette entries, aspect ratio, and background color of original gif
e->gif->SColorResolution = d->gif->SColorResolution;
e->gif->AspectByte = d->gif->AspectByte;

// Ensure background color is properly set
if (d->gif->SColorMap && d->gif->SBackGroundColor >= 0 &&
if (d->gif->SColorMap && d->gif->SBackGroundColor >= 0 &&
d->gif->SBackGroundColor < d->gif->SColorMap->ColorCount) {
e->gif->SBackGroundColor = d->gif->SBackGroundColor;
} else {
Expand All @@ -763,8 +811,8 @@ bool giflib_encoder_init(giflib_encoder e, const giflib_decoder d, int width, in
memmove(e->gif->SColorMap->Colors,
d->gif->SColorMap->Colors,
e->gif->SColorMap->ColorCount * sizeof(GifColorType));
if (d->gif->SBackGroundColor >= 0 &&

if (d->gif->SBackGroundColor >= 0 &&
d->gif->SBackGroundColor < d->gif->SColorMap->ColorCount) {
e->gif->SBackGroundColor = d->gif->SBackGroundColor;
} else {
Expand Down Expand Up @@ -838,12 +886,12 @@ static bool giflib_encoder_setup_frame(giflib_encoder e, const giflib_decoder d)
// This prevents incorrect removal of transparency when the background has transparency.
if (gcb.TransparentColor != NO_TRANSPARENT_COLOR) {
ColorMapObject* color_map = e->frame_color_map ? e->frame_color_map : e->gif->SColorMap;

// Only perform this optimization when using the global color map to avoid
// index mismatches between local and global palettes
if (color_map &&
if (color_map &&
!e->frame_color_map &&
gcb.TransparentColor == e->gif->SBackGroundColor &&
gcb.TransparentColor == e->gif->SBackGroundColor &&
d->bg_alpha == 255) {
gcb.TransparentColor = NO_TRANSPARENT_COLOR;
giflib_set_frame_gcb(e->gif, &gcb);
Expand Down