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Add avifRGBImage to the C++ API #3042

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Merged
vrabaud merged 3 commits into from
Feb 18, 2026
Merged

Add avifRGBImage to the C++ API #3042

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588e003
Add avifRGBImage to the C++ API
vrabaud Feb 17, 2026
876c872
Rename and add comment.
vrabaud Feb 17, 2026
efe1ca0
Simplify naming
vrabaud Feb 18, 2026
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11 changes: 7 additions & 4 deletions include/avif/avif_cxx.h
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Original file line number Diff line number Diff line change
Expand Up @@ -18,17 +18,20 @@ namespace avif
// Struct to call the destroy functions in a unique_ptr.
struct UniquePtrDeleter
{
void operator()(avifEncoder * encoder) const { avifEncoderDestroy(encoder); }
void operator()(avifDecoder * decoder) const { avifDecoderDestroy(decoder); }
void operator()(avifImage * image) const { avifImageDestroy(image); }
void operator()(avifEncoder * encoder) const { avifEncoderDestroy(encoder); }
void operator()(avifGainMap * gainMap) const { avifGainMapDestroy(gainMap); }
void operator()(avifImage * image) const { avifImageDestroy(image); }
void operator()(avifRGBImage * image) const { avifRGBImageFreePixels(image); }
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@wantehchang wantehchang Feb 18, 2026

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Vincent: This doesn't seem correct. avifRGBImageFreePixels() is implemented as follows:

void avifRGBImageFreePixels(avifRGBImage * rgb)
{
    if (rgb->pixels) {
        avifFree(rgb->pixels);
    }

    rgb->pixels = NULL;
    rgb->rowBytes = 0;
}

Note that it doesn't free the avifRGBImage struct. Could you modify an existing test in tests/gtest/ to show how avif::RGBImagePtr should be used?

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@vrabaud vrabaud Feb 19, 2026

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Fix at #3048

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@wantehchang wantehchang Feb 19, 2026

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Vincent: I thought about this class last night. I would like to suggest two alternatives.

The first alternative is to preserve the main functionality of RGBImagePtr but rename it RGBImageCleanup and define the class directly rather than using std::unique_ptr:

class RGBImageCleanup {
 public:
  RGBImageCleanup(avifRGBImage* rgb) : rgb_(rgb) {}
  ~RGBImageCleanup() { avifRGBImageFreePixels(rgb_); }
 private:
  avifRGBImage* rgb_ = nullptr;
};

By not using std::unique_ptr, we avoid the confusion caused by expecting it to free the avifRGBImage struct.

The second alternative is to derive a C++ RGBImage class from the C avifRGBImage struct. The destructor calls avifRGBImageFreePixels(this). The class may optionally provide constructors and methods such as AllocatePixels() for convenience.

My preference is the first alternative because it is the minimal solution to the cleanup problem. It is similar to absl::Cleanup (or its predecessor in Google's internal repository).

};

// Use these unique_ptr to ensure the structs are automatically destroyed.
using EncoderPtr = std::unique_ptr<avifEncoder, UniquePtrDeleter>;
using DecoderPtr = std::unique_ptr<avifDecoder, UniquePtrDeleter>;
using ImagePtr = std::unique_ptr<avifImage, UniquePtrDeleter>;
using EncoderPtr = std::unique_ptr<avifEncoder, UniquePtrDeleter>;
using GainMapPtr = std::unique_ptr<avifGainMap, UniquePtrDeleter>;
using ImagePtr = std::unique_ptr<avifImage, UniquePtrDeleter>;
// To use when RGBImage actually owns the pixels. RGBImage can also be used as a view, in which case it does not own the pixels.
using RGBImagePtr = std::unique_ptr<avifRGBImage, UniquePtrDeleter>;

} // namespace avif

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