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size apng frame buffer from png bit depth, not sBIT #238

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size apng frame buffer from png bit depth, not sBIT #238

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14 changes: 9 additions & 5 deletions third_party/apngdis/dec.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1013,20 +1013,24 @@ Status DecodeImageAPNG(const Span<const uint8_t> bytes,
png_color_8p sig_bits = nullptr;
// Error is OK -> sig_bits remains nullptr.
png_get_sBIT(ctx.png_ptr, ctx.info_ptr, &sig_bits);
const int png_bit_depth =
png_get_bit_depth(ctx.png_ptr, ctx.info_ptr);
SetColorData(ppf, png_get_color_type(ctx.png_ptr, ctx.info_ptr),
png_get_bit_depth(ctx.png_ptr, ctx.info_ptr), sig_bits,
png_bit_depth, sig_bits,
png_get_valid(ctx.png_ptr, ctx.info_ptr, PNG_INFO_tRNS));
num_channels =
ppf->info.num_color_channels + (ppf->info.alpha_bits ? 1 : 0);
// libpng emits native 16-bit samples for 16-bit PNGs; sBIT only
// lowers the reported bits_per_sample, so size the row buffer from
// the actual depth instead.
const bool is_16bit = png_bit_depth == 16;
format = {
/*num_channels=*/num_channels,
/*data_type=*/ppf->info.bits_per_sample > 8 ? JPEGLI_TYPE_UINT16
: JPEGLI_TYPE_UINT8,
/*data_type=*/is_16bit ? JPEGLI_TYPE_UINT16 : JPEGLI_TYPE_UINT8,
/*endianness=*/JPEGLI_BIG_ENDIAN,
/*align=*/0,
};
bytes_per_pixel =
num_channels * (format.data_type == JPEGLI_TYPE_UINT16 ? 2 : 1);
bytes_per_pixel = num_channels * (is_16bit ? 2 : 1);
// TODO(eustas): ensure multiplication is safe
uint64_t row_bytes =
static_cast<uint64_t>(image_rect.xsize()) * bytes_per_pixel;
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