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Allow odd clap dimensions and offsets
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The constraint in MIAF was replaced by an upsampling step before
cropping.
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@y-guyon
y-guyon committed Sep 10, 2024
1 parent 85979a7 commit e8fc905
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Showing 8 changed files with 105 additions and 56 deletions.
3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -25,6 +25,9 @@ The changes are relative to the previous release, unless the baseline is specifi
* Write an empty HandlerBox name field instead of "libavif" (saves 7 bytes).
* Update aom.cmd/LocalAom.cmake: v3.10.0
* Update svt.cmd/svt.sh/LocalSvt.cmake: v2.2.1
* 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 @@ -84,6 +84,7 @@ 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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3 changes: 2 additions & 1 deletion apps/avifenc.c
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Expand Up @@ -2290,9 +2290,10 @@ int main(int argc, char * argv[])

// Validate clap
avifCropRect cropRect;
avifBool upsampleBeforeCropping;
avifDiagnostics diag;
avifDiagnosticsClearError(&diag);
if (!avifCropRectConvertCleanApertureBox(&cropRect, &image->clap, image->width, image->height, image->yuvFormat, &diag)) {
if (!avifCropRectFromCleanApertureBox(&cropRect, &upsampleBeforeCropping, &image->clap, image->width, image->height, image->yuvFormat, &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,
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8 changes: 5 additions & 3 deletions apps/shared/avifutil.c
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Expand Up @@ -104,16 +104,18 @@ static void avifImageDumpInternal(const avifImage * avif,
printf("\n");

avifCropRect cropRect;
avifBool upsampleBeforeCropping;
avifDiagnostics diag;
avifDiagnosticsClearError(&diag);
avifBool validClap =
avifCropRectConvertCleanApertureBox(&cropRect, &avif->clap, avif->width, avif->height, avif->yuvFormat, &diag);
avifCropRectFromCleanApertureBox(&cropRect, &upsampleBeforeCropping, &avif->clap, avif->width, avif->height, avif->yuvFormat, &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,
upsampleBeforeCropping ? " (upsample before cropping)" : "");
} else {
printf(" * Invalid: %s\n", diag.error);
}
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23 changes: 16 additions & 7 deletions include/avif/avif.h
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Expand Up @@ -460,6 +460,8 @@ typedef struct avifPixelAspectRatioBox
typedef struct avifCleanApertureBox
{
// 'clap' from ISO/IEC 14496-12:2015 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 exact clean aperture width, in counted pixels, of the video image
uint32_t widthN;
Expand Down Expand Up @@ -516,19 +518,26 @@ 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);
// If upsampleBeforeCropping is 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 avifCropRectFromCleanApertureBox(avifCropRect * cropRect,
avifBool * upsampleBeforeCropping,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag);
AVIF_NODISCARD AVIF_API avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
const avifCropRect * cropRect,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag);

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

// ---------------------------------------------------------------------------
// avifContentLightLevelInformationBox

Expand Down Expand Up @@ -1113,7 +1122,7 @@ 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),

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74 changes: 41 additions & 33 deletions src/avif.c
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Expand Up @@ -670,19 +670,8 @@ 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 @@ -692,28 +681,16 @@ 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,
avifBool * upsampleBeforeCropping,
const avifCleanApertureBox * clap,
uint32_t imageW,
uint32_t imageH,
avifPixelFormat yuvFormat,
avifDiagnostics * diag)
{
avifDiagnosticsClearError(diag);

Expand All @@ -722,6 +699,16 @@ avifBool avifCropRectConvertCleanApertureBox(avifCropRect * cropRect,
// positive or negative. For cleanApertureWidth and cleanApertureHeight,
// N shall be positive and D shall be strictly positive.

// ISO/IEC 23000-22:2024, 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;
// - 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

const int32_t widthN = (int32_t)clap->widthN;
const int32_t widthD = (int32_t)clap->widthD;
const int32_t heightN = (int32_t)clap->heightN;
Expand Down Expand Up @@ -810,7 +797,27 @@ 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);
if (!avifCropRectIsValid(cropRect, imageW, imageH, diag)) {
return AVIF_FALSE;
}

*upsampleBeforeCropping = ((yuvFormat == AVIF_PIXEL_FORMAT_YUV420 || yuvFormat == AVIF_PIXEL_FORMAT_YUV422) &&
(cropRect->width % 2 || cropRect->x % 2)) ||
(yuvFormat == AVIF_PIXEL_FORMAT_YUV420 && (cropRect->height % 2 || cropRect->y % 2));
return AVIF_TRUE;
}

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

avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
Expand All @@ -820,9 +827,10 @@ avifBool avifCleanApertureBoxConvertCropRect(avifCleanApertureBox * clap,
avifPixelFormat yuvFormat,
avifDiagnostics * diag)
{
(void)yuvFormat;
avifDiagnosticsClearError(diag);

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

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4 changes: 3 additions & 1 deletion src/read.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1253,10 +1253,12 @@ static avifResult avifDecoderItemValidateProperties(const avifDecoderItem * item
}

avifCropRect cropRect;
avifBool upsampleBeforeCropping;
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, &upsampleBeforeCropping, &clapProp->u.clap, imageW, imageH, configFormat, diag);
if (!validClap) {
return AVIF_RESULT_BMFF_PARSE_FAILED;
}
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45 changes: 34 additions & 11 deletions tests/gtest/avifclaptest.cc
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Expand Up @@ -82,14 +82,15 @@ using InvalidClapPropertyTest =
INSTANTIATE_TEST_SUITE_P(Parameterized, InvalidClapPropertyTest,
::testing::ValuesIn(kInvalidClapPropertyTestParams));

// Negative tests for the avifCropRectConvertCleanApertureBox() function.
// Negative tests for the avifCropRectFromCleanApertureBox() function.
TEST_P(InvalidClapPropertyTest, ValidateClapProperty) {
const InvalidClapPropertyParam& param = GetParam();
avifCropRect crop_rect;
avifBool upsampleBeforeCropping;
avifDiagnostics diag;
EXPECT_FALSE(avifCropRectConvertCleanApertureBox(&crop_rect, &param.clap,
param.width, param.height,
param.yuv_format, &diag));
EXPECT_FALSE(avifCropRectFromCleanApertureBox(
&crop_rect, &upsampleBeforeCropping, &param.clap, param.width,
param.height, param.yuv_format, &diag));
}

struct ValidClapPropertyParam {
Expand All @@ -99,6 +100,7 @@ struct ValidClapPropertyParam {
avifCleanApertureBox clap;

avifCropRect expected_crop_rect;
bool expected_upsample_before_cropping;
};

constexpr ValidClapPropertyParam kValidClapPropertyTestParams[] = {
Expand All @@ -110,7 +112,8 @@ constexpr ValidClapPropertyParam kValidClapPropertyTestParams[] = {
160,
AVIF_PIXEL_FORMAT_YUV420,
{96, 1, 132, 1, 0, 1, 0, 1},
{12, 14, 96, 132}},
{12, 14, 96, 132},
false},
// pcX = -30 + (120 - 1)/2 = 29.5
// pcY = -40 + (160 - 1)/2 = 39.5
// leftmost = 29.5 - (60 - 1)/2 = 0
Expand All @@ -120,7 +123,8 @@ constexpr ValidClapPropertyParam kValidClapPropertyTestParams[] = {
AVIF_PIXEL_FORMAT_YUV420,
{60, 1, 80, 1, static_cast<uint32_t>(-30), 1, static_cast<uint32_t>(-40),
1},
{0, 0, 60, 80}},
{0, 0, 60, 80},
false},
// pcX = -1/2 + (100 - 1)/2 = 49
// pcY = -1/2 + (100 - 1)/2 = 49
// leftmost = 49 - (99 - 1)/2 = 0
Expand All @@ -129,27 +133,46 @@ constexpr ValidClapPropertyParam kValidClapPropertyTestParams[] = {
100,
AVIF_PIXEL_FORMAT_YUV420,
{99, 1, 99, 1, static_cast<uint32_t>(-1), 2, static_cast<uint32_t>(-1), 2},
{0, 0, 99, 99}},
{0, 0, 99, 99},
true},
// pcX = -1/2 + (100 - 1)/2 = 49
// pcY = -1/2 + (100 - 1)/2 = 49
// leftmost = 49 - (99 - 1)/2 = 0
// topmost = 49 - (99 - 1)/2 = 0
{100,
100,
AVIF_PIXEL_FORMAT_YUV420,
{99, 1, 99, 1, 1, 2, 1, 2},
{1, 1, 99, 99},
true},
};

using ValidClapPropertyTest = ::testing::TestWithParam<ValidClapPropertyParam>;

INSTANTIATE_TEST_SUITE_P(Parameterized, ValidClapPropertyTest,
::testing::ValuesIn(kValidClapPropertyTestParams));

// Positive tests for the avifCropRectConvertCleanApertureBox() function.
// Positive tests for the avifCropRectFromCleanApertureBox() function.
TEST_P(ValidClapPropertyTest, ValidateClapProperty) {
const ValidClapPropertyParam& param = GetParam();
avifCropRect crop_rect;
avifBool upsampleBeforeCropping;
avifDiagnostics diag;
EXPECT_TRUE(avifCropRectConvertCleanApertureBox(&crop_rect, &param.clap,
param.width, param.height,
param.yuv_format, &diag))
EXPECT_TRUE(avifCropRectFromCleanApertureBox(
&crop_rect, &upsampleBeforeCropping, &param.clap, param.width,
param.height, param.yuv_format, &diag))
<< diag.error;
EXPECT_EQ(crop_rect.x, param.expected_crop_rect.x);
EXPECT_EQ(crop_rect.y, param.expected_crop_rect.y);
EXPECT_EQ(crop_rect.width, param.expected_crop_rect.width);
EXPECT_EQ(crop_rect.height, param.expected_crop_rect.height);
EXPECT_EQ(upsampleBeforeCropping, param.expected_upsample_before_cropping);

// Deprecated function coverage.
EXPECT_EQ(avifCropRectConvertCleanApertureBox(&crop_rect, &param.clap,
param.width, param.height,
param.yuv_format, &diag),
!upsampleBeforeCropping);
}

} // namespace

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