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Allow odd clap dimensions and offsets #2426

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Allow odd clap dimensions and offsets #2426

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0e4343c
Allow odd clap dimensions and offsets
y-guyon Sep 10, 2024
73a91d8
Move oddness check to CropRectRequiresUpsampling()
y-guyon Nov 22, 2024
7766d13
Remove unused variable
y-guyon Nov 22, 2024
858b0cd
Inline avifCodecConfigurationBoxGetFormat()
y-guyon Nov 22, 2024
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -37,6 +37,9 @@ The changes are relative to the previous release, unless the baseline is specifi
avifGainMapMetadataDouble structs.
* Add avif(Un)SignedFraction structs and avifDoubleTo(Un)SignedFraction
utility functions.
* Allow decoding subsampled images with odd Clean Aperture dimensions or offsets.
* Deprecate avifCropRectConvertCleanApertureBox(). Replace it with
avifCropRectFromCleanApertureBox().

## [1.1.1] - 2024-07-30

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1 change: 1 addition & 0 deletions android_jni/avifandroidjni/src/main/jni/libavif_jni.cc
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Expand Up @@ -85,6 +85,7 @@ bool CreateDecoderAndParse(AvifDecoderWrapper* const decoder,
avifDiagnostics diag;
// If the image does not have a valid 'clap' property, then we simply display
// the whole image.
// TODO: Use avifCropRectFromCleanApertureBox() instead.
if (!(decoder->decoder->image->transformFlags & AVIF_TRANSFORM_CLAP) ||
!avifCropRectConvertCleanApertureBox(
&decoder->crop, &decoder->decoder->image->clap,
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18 changes: 18 additions & 0 deletions apps/avifdec.c
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Expand Up @@ -347,6 +347,24 @@ int main(int argc, char * argv[])
printf("Image details:\n");
avifImageDump(decoder->image, 0, 0, decoder->progressiveState);

if (decoder->image->transformFlags & AVIF_TRANSFORM_CLAP) {
avifCropRect cropRect;
if (avifCropRectFromCleanApertureBox(&cropRect,
&decoder->image->clap,
decoder->image->width,
decoder->image->height,
&decoder->diag)) {
if (cropRect.x != 0 || cropRect.y != 0 || cropRect.width != decoder->image->width ||
cropRect.height != decoder->image->height) {
// TODO: Implement, see https://github.com/AOMediaCodec/libavif/issues/2427
fprintf(stderr, "Warning: Clean Aperture values were ignored, the output image was NOT cropped\n");
}
} else {
// Should happen only if AVIF_STRICT_CLAP_VALID is disabled.
fprintf(stderr, "Warning: Invalid Clean Aperture values\n");
}
}

if (ignoreICC && (decoder->image->icc.size > 0)) {
printf("[--ignore-icc] Discarding ICC profile.\n");
// This cannot fail.
Expand Down
3 changes: 2 additions & 1 deletion apps/avifenc.c
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Expand Up @@ -2292,7 +2292,7 @@ int main(int argc, char * argv[])
avifCropRect cropRect;
avifDiagnostics diag;
avifDiagnosticsClearError(&diag);
if (!avifCropRectConvertCleanApertureBox(&cropRect, &image->clap, image->width, image->height, image->yuvFormat, &diag)) {
if (!avifCropRectFromCleanApertureBox(&cropRect, &image->clap, image->width, image->height, &diag)) {
fprintf(stderr,
"ERROR: Invalid clap: width:[%d / %d], height:[%d / %d], horizOff:[%d / %d], vertOff:[%d / %d] - %s\n",
(int32_t)image->clap.widthN,
Expand All @@ -2306,6 +2306,7 @@ int main(int argc, char * argv[])
diag.error);
goto cleanup;
}
// avifCropRectRequiresUpsampling() does not need to be called for clap validation.
}
if (irotAngle != 0xff) {
image->transformFlags |= AVIF_TRANSFORM_IROT;
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8 changes: 4 additions & 4 deletions apps/shared/avifutil.c
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Expand Up @@ -101,14 +101,14 @@ static void avifImageDumpInternal(const avifImage * avif, uint32_t gridCols, uin
avifCropRect cropRect;
avifDiagnostics diag;
avifDiagnosticsClearError(&diag);
avifBool validClap =
avifCropRectConvertCleanApertureBox(&cropRect, &avif->clap, avif->width, avif->height, avif->yuvFormat, &diag);
avifBool validClap = avifCropRectFromCleanApertureBox(&cropRect, &avif->clap, avif->width, avif->height, &diag);
if (validClap) {
printf(" * Valid, derived crop rect: X: %d, Y: %d, W: %d, H: %d\n",
printf(" * Valid, derived crop rect: X: %d, Y: %d, W: %d, H: %d%s\n",
cropRect.x,
cropRect.y,
cropRect.width,
cropRect.height);
cropRect.height,
avifCropRectRequiresUpsampling(&cropRect, avif->yuvFormat) ? " (upsample before cropping)" : "");
} else {
printf(" * Invalid: %s\n", diag.error);
}
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22 changes: 15 additions & 7 deletions include/avif/avif.h
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Expand Up @@ -486,6 +486,8 @@ typedef struct avifPixelAspectRatioBox
typedef struct avifCleanApertureBox
{
// 'clap' from ISO/IEC 14496-12:2022 12.1.4.3
// Note that ISO/IEC 23000-22:2024 7.3.6.7 requires the decoded image to be upsampled to 4:4:4 before
// clean aperture is applied if a clean aperture size or offset is odd in a subsampled dimension.

// a fractional number which defines the width of the clean aperture image
uint32_t widthN;
Expand Down Expand Up @@ -544,18 +546,24 @@ typedef struct avifCropRect

// These will return AVIF_FALSE if the resultant values violate any standards, and if so, the output
// values are not guaranteed to be complete or correct and should not be used.
AVIF_NODISCARD AVIF_API avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag);
AVIF_NODISCARD AVIF_API avifBool avifCropRectFromCleanApertureBox(avifCropRect * cropRect,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifDiagnostics * diag);
AVIF_NODISCARD AVIF_API avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
const avifCropRect * cropRect,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag);
// If this function returns true, the image must be upsampled from 4:2:0 or 4:2:2 to 4:4:4 before
// Clean Aperture values are applied.
AVIF_NODISCARD AVIF_API avifBool avifCropRectRequiresUpsampling(const avifCropRect * cropRect, avifPixelFormat yuvFormat);

// Deprecated. Use avifCropRectFromCleanApertureBox() instead.
AVIF_NODISCARD AVIF_API avifBool
avifCropRectConvertCleanApertureBox(avifCropRect *, const avifCleanApertureBox *, uint32_t, uint32_t, avifPixelFormat, avifDiagnostics *);

// ---------------------------------------------------------------------------
// avifContentLightLevelInformationBox
Expand Down Expand Up @@ -1116,7 +1124,7 @@ typedef enum avifStrictFlag
AVIF_STRICT_PIXI_REQUIRED = (1 << 0),

// This demands that the values surfaced in the clap box are valid, determined by attempting to
// convert the clap box to a crop rect using avifCropRectConvertCleanApertureBox(). If this
// convert the clap box to a crop rect using avifCropRectFromCleanApertureBox(). If this
// function returns AVIF_FALSE and this strict flag is set, the decode will fail.
AVIF_STRICT_CLAP_VALID = (1 << 1),

Expand Down
84 changes: 48 additions & 36 deletions src/avif.c
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Expand Up @@ -735,19 +735,8 @@ static avifBool overflowsInt32(int64_t x)
return (x < INT32_MIN) || (x > INT32_MAX);
}

static avifBool avifCropRectIsValid(const avifCropRect * cropRect, uint32_t imageW, uint32_t imageH, avifPixelFormat yuvFormat, avifDiagnostics * diag)

static avifBool avifCropRectIsValid(const avifCropRect * cropRect, uint32_t imageW, uint32_t imageH, avifDiagnostics * diag)
{
// ISO/IEC 23000-22:2019/Amd. 2:2021, Section 7.3.6.7:
// The clean aperture property is restricted according to the chroma
// sampling format of the input image (4:4:4, 4:2:2:, 4:2:0, or 4:0:0) as
// follows:
// ...
// - If chroma is subsampled horizontally (i.e., 4:2:2 and 4:2:0), the
// leftmost pixel of the clean aperture shall be even numbers;
// - If chroma is subsampled vertically (i.e., 4:2:0), the topmost line
// of the clean aperture shall be even numbers.

if ((cropRect->width == 0) || (cropRect->height == 0)) {
avifDiagnosticsPrintf(diag, "[Strict] crop rect width and height must be nonzero");
return AVIF_FALSE;
Expand All @@ -757,28 +746,14 @@ static avifBool avifCropRectIsValid(const avifCropRect * cropRect, uint32_t imag
avifDiagnosticsPrintf(diag, "[Strict] crop rect is out of the image's bounds");
return AVIF_FALSE;
}

if ((yuvFormat == AVIF_PIXEL_FORMAT_YUV420) || (yuvFormat == AVIF_PIXEL_FORMAT_YUV422)) {
if ((cropRect->x % 2) != 0) {
avifDiagnosticsPrintf(diag, "[Strict] crop rect X offset must be even due to this image's YUV subsampling");
return AVIF_FALSE;
}
}
if (yuvFormat == AVIF_PIXEL_FORMAT_YUV420) {
if ((cropRect->y % 2) != 0) {
avifDiagnosticsPrintf(diag, "[Strict] crop rect Y offset must be even due to this image's YUV subsampling");
return AVIF_FALSE;
}
}
return AVIF_TRUE;
}

avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag)
avifBool avifCropRectFromCleanApertureBox(avifCropRect * cropRect,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifDiagnostics * diag)
{
avifDiagnosticsClearError(diag);

Expand All @@ -805,9 +780,6 @@ avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
}

// ISO/IEC 23000-22:2019/Amd. 2:2021, Section 7.3.6.7:
// The clean aperture property is restricted according to the chroma
// sampling format of the input image (4:4:4, 4:2:2:, 4:2:0, or 4:0:0) as
// follows:
// - cleanApertureWidth and cleanApertureHeight shall be integers;
// - The leftmost pixel and the topmost line of the clean aperture as
// defined in ISO/IEC 14496-12:2020, Section 12.1.4.1 shall be integers;
Expand Down Expand Up @@ -884,7 +856,46 @@ avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
cropRect->y = (uint32_t)(cropY.n / cropY.d);
cropRect->width = (uint32_t)clapW;
cropRect->height = (uint32_t)clapH;
return avifCropRectIsValid(cropRect, imageW, imageH, yuvFormat, diag);
return avifCropRectIsValid(cropRect, imageW, imageH, diag);
}

avifBool avifCropRectRequiresUpsampling(const avifCropRect * cropRect, avifPixelFormat yuvFormat)
{
// ISO/IEC 23000-22:2024 FDIS, Section 7.3.6.7:
// - If any of the following conditions hold true, the image is first implicitly upsampled to 4:4:4:
// - chroma is subsampled horizontally (i.e., 4:2:2 and 4:2:0) and cleanApertureWidth is odd
// - chroma is subsampled horizontally (i.e., 4:2:2 and 4:2:0) and left-most pixel is on an odd position
// - chroma is subsampled vertically (i.e., 4:2:0) and cleanApertureHeight is odd
// - chroma is subsampled vertically (i.e., 4:2:0) and topmost line is on an odd position

// AV1 supports odd dimensions with chroma subsampling in those directions, so only look for x and y.
return ((yuvFormat == AVIF_PIXEL_FORMAT_YUV420 || yuvFormat == AVIF_PIXEL_FORMAT_YUV422) && (cropRect->x % 2)) ||
(yuvFormat == AVIF_PIXEL_FORMAT_YUV420 && (cropRect->y % 2));
}

avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag)
{
if (avifCropRectFromCleanApertureBox(cropRect, clap, imageW, imageH, diag)) {
// Keep the same pre-deprecation behavior.

// ISO/IEC 23000-22:2019/Amd. 2:2021, Section 7.3.6.7:
// - If chroma is subsampled horizontally (i.e., 4:2:2 and 4:2:0),
// the leftmost pixel of the clean aperture shall be even numbers;
// - If chroma is subsampled vertically (i.e., 4:2:0),
// the topmost line of the clean aperture shall be even numbers.

if (avifCropRectRequiresUpsampling(cropRect, yuvFormat)) {
avifDiagnosticsPrintf(diag, "[Strict] crop rect X and Y offsets must be even due to this image's YUV subsampling");
return AVIF_FALSE;
}
return AVIF_TRUE;
}
return AVIF_FALSE;
}

avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
Expand All @@ -894,9 +905,10 @@ avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
avifPixelFormat yuvFormat,
avifDiagnostics * diag)
{
(void)yuvFormat;
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avifDiagnosticsClearError(diag);

if (!avifCropRectIsValid(cropRect, imageW, imageH, yuvFormat, diag)) {
if (!avifCropRectIsValid(cropRect, imageW, imageH, diag)) {
return AVIF_FALSE;
}

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32 changes: 14 additions & 18 deletions src/read.c
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Expand Up @@ -367,19 +367,6 @@ static uint32_t avifCodecConfigurationBoxGetDepth(const avifCodecConfigurationBo
return 8;
}

// This is used as a hint to validating the clap box in avifDecoderItemValidateProperties.
static avifPixelFormat avifCodecConfigurationBoxGetFormat(const avifCodecConfigurationBox * av1C)
{
if (av1C->monochrome) {
return AVIF_PIXEL_FORMAT_YUV400;
} else if (av1C->chromaSubsamplingY == 1) {
return AVIF_PIXEL_FORMAT_YUV420;
} else if (av1C->chromaSubsamplingX == 1) {
return AVIF_PIXEL_FORMAT_YUV422;
}
return AVIF_PIXEL_FORMAT_YUV444;
}

static const avifPropertyArray * avifSampleTableGetProperties(const avifSampleTable * sampleTable, avifCodecType codecType)
{
for (uint32_t i = 0; i < sampleTable->sampleDescriptions.count; ++i) {
Expand Down Expand Up @@ -1231,9 +1218,19 @@ static avifResult avifDecoderItemValidateProperties(const avifDecoderItem * item
if (item->miniBoxPixelFormat != AVIF_PIXEL_FORMAT_NONE) {
// This is a MinimizedImageBox ('mini').

if (item->miniBoxPixelFormat != avifCodecConfigurationBoxGetFormat(&configProp->u.av1C)) {
avifPixelFormat av1CPixelFormat;
if (configProp->u.av1C.monochrome) {
av1CPixelFormat = AVIF_PIXEL_FORMAT_YUV400;
} else if (configProp->u.av1C.chromaSubsamplingY == 1) {
av1CPixelFormat = AVIF_PIXEL_FORMAT_YUV420;
} else if (configProp->u.av1C.chromaSubsamplingX == 1) {
av1CPixelFormat = AVIF_PIXEL_FORMAT_YUV422;
} else {
av1CPixelFormat = AVIF_PIXEL_FORMAT_YUV444;
}
if (item->miniBoxPixelFormat != av1CPixelFormat) {
if (!memcmp(configPropName, "av2C", 4) && item->miniBoxPixelFormat == AVIF_PIXEL_FORMAT_YUV400 &&
avifCodecConfigurationBoxGetFormat(&configProp->u.av1C) == AVIF_PIXEL_FORMAT_YUV420) {
av1CPixelFormat == AVIF_PIXEL_FORMAT_YUV420) {
// avm does not handle monochrome as of research-v8.0.0.
// 4:2:0 is used instead.
} else {
Expand All @@ -1242,7 +1239,7 @@ static avifResult avifDecoderItemValidateProperties(const avifDecoderItem * item
item->id,
avifPixelFormatToString(item->miniBoxPixelFormat),
configPropName,
avifPixelFormatToString(avifCodecConfigurationBoxGetFormat(&configProp->u.av1C)));
avifPixelFormatToString(av1CPixelFormat));
return AVIF_RESULT_BMFF_PARSE_FAILED;
}
}
Expand Down Expand Up @@ -1279,8 +1276,7 @@ static avifResult avifDecoderItemValidateProperties(const avifDecoderItem * item
avifCropRect cropRect;
const uint32_t imageW = ispeProp->u.ispe.width;
const uint32_t imageH = ispeProp->u.ispe.height;
const avifPixelFormat configFormat = avifCodecConfigurationBoxGetFormat(&configProp->u.av1C);
avifBool validClap = avifCropRectConvertCleanApertureBox(&cropRect, &clapProp->u.clap, imageW, imageH, configFormat, diag);
const avifBool validClap = avifCropRectFromCleanApertureBox(&cropRect, &clapProp->u.clap, imageW, imageH, diag);
if (!validClap) {
return AVIF_RESULT_BMFF_PARSE_FAILED;
}
Expand Down
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