Function avifDecoderCheckAlphaProperties

src/read.c:5921–5964

}

static avifResult avifDecoderCheckAlphaProperties(avifDecoder * decoder, const avifPropertyArray * alphaProperties)
{
    const avifImage * image = decoder->image;
    // The 'clap', 'irot' and 'imir' transformative properties should be applied to the alpha
    // auxiliary image item before considering it a plane of the color image item.
    // Alternatively, inequality with the transformative properties attached to the color image item
    // should be treated as AVIF_RESULT_NOT_IMPLEMENTED.
    // The latter is easier and is the behavior of libavif.

    const avifProperty * clapProp = avifPropertyArrayFind(alphaProperties, "clap");
    const avifProperty * irotProp = avifPropertyArrayFind(alphaProperties, "irot");
    const avifProperty * imirProp = avifPropertyArrayFind(alphaProperties, "imir");
    if (clapProp == NULL && irotProp == NULL && imirProp == NULL) {
        // However, libavif up to version 1.3.0 generated images lacking transformative property
        // associations with alpha auxiliary image items, so be lenient on their absence for
        // backward compatibility with previously generated images.
        return AVIF_RESULT_OK;
    }

    // HEIF (ISO/IEC 23008-12), Section 6.9.1:
    //   When the width or the height of the alpha plane differs from the width or the height of the
    //   master image, respectively, the alpha plane is resized to have the same width and height as
    //   those of the master image.
    // There is no need to enforce specific 'ispe' values describing the alpha item because
    // the alpha item must be resized to the dimensions of the associated color item.

    if (!clapProp != !(image->transformFlags & AVIF_TRANSFORM_CLAP) ||
        (clapProp && (clapProp->u.clap.widthN != image->clap.widthN || clapProp->u.clap.widthD != image->clap.widthD ||
                      clapProp->u.clap.heightN != image->clap.heightN || clapProp->u.clap.heightD != image->clap.heightD ||
                      clapProp->u.clap.horizOffN != image->clap.horizOffN || clapProp->u.clap.horizOffD != image->clap.horizOffD ||
                      clapProp->u.clap.vertOffN != image->clap.vertOffN || clapProp->u.clap.vertOffD != image->clap.vertOffD))) {
        avifDiagnosticsPrintf(&decoder->diag, "Clean aperture property mismatch between alpha auxiliary image item and color item");
        return AVIF_RESULT_NOT_IMPLEMENTED;
    }
    if (!irotProp != !(image->transformFlags & AVIF_TRANSFORM_IROT) || (irotProp && irotProp->u.irot.angle != image->irot.angle)) {
        avifDiagnosticsPrintf(&decoder->diag, "Rotation property mismatch between alpha auxiliary image item and color item");
        return AVIF_RESULT_NOT_IMPLEMENTED;
    }
    if (!imirProp != !(image->transformFlags & AVIF_TRANSFORM_IMIR) || (imirProp && imirProp->u.imir.axis != image->imir.axis)) {
        avifDiagnosticsPrintf(&decoder->diag, "Mirroring property mismatch between alpha auxiliary image item and color item");
        return AVIF_RESULT_NOT_IMPLEMENTED;
    }
    return AVIF_RESULT_OK;
}

static avifResult avifDecoderCheckGainMapProperties(avifDecoder * decoder, const avifPropertyArray * gainMapProperties)
{