apps/shared/avifutil.c - libavif - Git at Google

 // Copyright 2019 Joe Drago. All rights reserved.
 // SPDX-License-Identifier: BSD-2-Clause

 #include "avifutil.h"

 #include <ctype.h>
 #include <stdio.h>
 #include <string.h>

 #include "avifjpeg.h"
 #include "avifpng.h"
 #include "y4m.h"

 // |a| and |b| hold int32_t values. The int64_t type is used so that we can negate INT32_MIN without
 // overflowing int32_t.
 static int64_t calcGCD(int64_t a, int64_t b)
 {
     if (a < 0) {
         a *= -1;
     }
     if (b < 0) {
         b *= -1;
     }
     while (b != 0) {
         int64_t r = a % b;
         a = b;
         b = r;
     }
     return a;
 }

 static void printClapFraction(const char * name, int32_t n, int32_t d)
 {
     printf("%s: %d/%d", name, n, d);
     if (d != 0) {
         int64_t gcd = calcGCD(n, d);
         if (gcd > 1) {
             int32_t rn = (int32_t)(n / gcd);
             int32_t rd = (int32_t)(d / gcd);
             printf(" (%d/%d)", rn, rd);
         }
     }
 }

 static void avifImageDumpInternal(const avifImage * avif, uint32_t gridCols, uint32_t gridRows, avifBool alphaPresent, avifProgressiveState progressiveState)
 {
     uint32_t width = avif->width;
     uint32_t height = avif->height;
     if (gridCols && gridRows) {
         width *= gridCols;
         height *= gridRows;
     }
     printf(" * Resolution     : %ux%u\n", width, height);
     printf(" * Bit Depth      : %u\n", avif->depth);
     printf(" * Format         : %s\n", avifPixelFormatToString(avif->yuvFormat));
     if (avif->yuvFormat == AVIF_PIXEL_FORMAT_YUV420) {
         printf(" * Chroma Sam. Pos: %u\n", avif->yuvChromaSamplePosition);
     }
     printf(" * Alpha          : %s\n", alphaPresent ? (avif->alphaPremultiplied ? "Premultiplied" : "Not premultiplied") : "Absent");
     printf(" * Range          : %s\n", (avif->yuvRange == AVIF_RANGE_FULL) ? "Full" : "Limited");

     printf(" * Color Primaries: %u\n", avif->colorPrimaries);
     printf(" * Transfer Char. : %u\n", avif->transferCharacteristics);
     printf(" * Matrix Coeffs. : %u\n", avif->matrixCoefficients);

     if (avif->icc.size != 0) {
         printf(" * ICC Profile    : Present (%" AVIF_FMT_ZU " bytes)\n", avif->icc.size);
     } else {
         printf(" * ICC Profile    : Absent\n");
     }
     if (avif->xmp.size != 0) {
         printf(" * XMP Metadata   : Present (%" AVIF_FMT_ZU " bytes)\n", avif->xmp.size);
     } else {
         printf(" * XMP Metadata   : Absent\n");
     }
     if (avif->exif.size != 0) {
         printf(" * Exif Metadata  : Present (%" AVIF_FMT_ZU " bytes)\n", avif->exif.size);
     } else {
         printf(" * Exif Metadata  : Absent\n");
     }

     if (avif->transformFlags == AVIF_TRANSFORM_NONE) {
         printf(" * Transformations: None\n");
     } else {
         printf(" * Transformations:\n");

         if (avif->transformFlags & AVIF_TRANSFORM_PASP) {
             printf("    * pasp (Aspect Ratio)  : %d/%d\n", (int)avif->pasp.hSpacing, (int)avif->pasp.vSpacing);
         }
         if (avif->transformFlags & AVIF_TRANSFORM_CLAP) {
             printf("    * clap (Clean Aperture): ");
             printClapFraction("W", (int32_t)avif->clap.widthN, (int32_t)avif->clap.widthD);
             printf(", ");
             printClapFraction("H", (int32_t)avif->clap.heightN, (int32_t)avif->clap.heightD);
             printf(", ");
             printClapFraction("hOff", (int32_t)avif->clap.horizOffN, (int32_t)avif->clap.horizOffD);
             printf(", ");
             printClapFraction("vOff", (int32_t)avif->clap.vertOffN, (int32_t)avif->clap.vertOffD);
             printf("\n");

             avifCropRect cropRect;
             avifDiagnostics diag;
             avifDiagnosticsClearError(&diag);
             avifBool validClap =
                 avifCropRectConvertCleanApertureBox(&cropRect, &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",
                        cropRect.x,
                        cropRect.y,
                        cropRect.width,
                        cropRect.height);
             } else {
                 printf("      * Invalid: %s\n", diag.error);
             }
         }
         if (avif->transformFlags & AVIF_TRANSFORM_IROT) {
             printf("    * irot (Rotation)      : %u\n", avif->irot.angle);
         }
         if (avif->transformFlags & AVIF_TRANSFORM_IMIR) {
             printf("    * imir (Mirror)        : %u (%s)\n", avif->imir.axis, (avif->imir.axis == 0) ? "top-to-bottom" : "left-to-right");
         }
     }
     printf(" * Progressive    : %s\n", avifProgressiveStateToString(progressiveState));
     if (avif->clli.maxCLL > 0 || avif->clli.maxPALL > 0) {
         printf(" * CLLI           : %hu, %hu\n", avif->clli.maxCLL, avif->clli.maxPALL);
     }
 }

 void avifImageDump(const avifImage * avif, uint32_t gridCols, uint32_t gridRows, avifProgressiveState progressiveState)
 {
     const avifBool alphaPresent = avif->alphaPlane && (avif->alphaRowBytes > 0);
     avifImageDumpInternal(avif, gridCols, gridRows, alphaPresent, progressiveState);
 }

 void avifContainerDump(const avifDecoder * decoder)
 {
     avifImageDumpInternal(decoder->image, 0, 0, decoder->alphaPresent, decoder->progressiveState);
     if ((decoder->progressiveState == AVIF_PROGRESSIVE_STATE_UNAVAILABLE) && (decoder->imageCount > 1)) {
         if (decoder->repetitionCount == AVIF_REPETITION_COUNT_INFINITE) {
             printf(" * Repeat Count   : Infinite\n");
         } else if (decoder->repetitionCount == AVIF_REPETITION_COUNT_UNKNOWN) {
             printf(" * Repeat Count   : Unknown\n");
         } else {
             printf(" * Repeat Count   : %d\n", decoder->repetitionCount);
         }
     }
 }

 void avifPrintVersions(void)
 {
     char codecVersions[256];
     avifCodecVersions(codecVersions);
     printf("Version: %s (%s)\n", avifVersion(), codecVersions);

     unsigned int libyuvVersion = avifLibYUVVersion();
     if (libyuvVersion == 0) {
         printf("libyuv : unavailable\n");
     } else {
         printf("libyuv : available (%u)\n", libyuvVersion);
     }

     printf("\n");
 }

 avifAppFileFormat avifGuessFileFormat(const char * filename)
 {
     // Guess from the file header
     FILE * f = fopen(filename, "rb");
     if (f) {
         uint8_t headerBuffer[144];
         size_t bytesRead = fread(headerBuffer, 1, sizeof(headerBuffer), f);
         fclose(f);

         if (bytesRead > 0) {
             avifROData header;
             header.data = headerBuffer;
             header.size = bytesRead;

             if (avifPeekCompatibleFileType(&header)) {
                 return AVIF_APP_FILE_FORMAT_AVIF;
             }

             static const uint8_t signatureJPEG[2] = { 0xFF, 0xD8 };
             static const uint8_t signaturePNG[8] = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
             static const uint8_t signatureY4M[9] = { 0x59, 0x55, 0x56, 0x34, 0x4D, 0x50, 0x45, 0x47, 0x32 }; // "YUV4MPEG2"
             struct avifHeaderSignature
             {
                 avifAppFileFormat format;
                 const uint8_t * magic;
                 size_t magicSize;
             } signatures[] = { { AVIF_APP_FILE_FORMAT_JPEG, signatureJPEG, sizeof(signatureJPEG) },
                                { AVIF_APP_FILE_FORMAT_PNG, signaturePNG, sizeof(signaturePNG) },
                                { AVIF_APP_FILE_FORMAT_Y4M, signatureY4M, sizeof(signatureY4M) } };
             const size_t signaturesCount = sizeof(signatures) / sizeof(signatures[0]);

             for (size_t signatureIndex = 0; signatureIndex < signaturesCount; ++signatureIndex) {
                 struct avifHeaderSignature * signature = &signatures[signatureIndex];
                 if (header.size < signature->magicSize) {
                     continue;
                 }
                 if (!memcmp(header.data, signature->magic, signature->magicSize)) {
                     return signature->format;
                 }
             }

             // If none of these signatures match, bail out here. Guessing by extension won't help.
             return AVIF_APP_FILE_FORMAT_UNKNOWN;
         }
     }

     // If we get here, the file header couldn't be read for some reason. Guess from the extension.

     const char * fileExt = strrchr(filename, '.');
     if (!fileExt) {
         return AVIF_APP_FILE_FORMAT_UNKNOWN;
     }
     ++fileExt; // skip past the dot

     char lowercaseExt[8]; // This only needs to fit up to "jpeg", so this is plenty
     const size_t fileExtLen = strlen(fileExt);
     if (fileExtLen >= sizeof(lowercaseExt)) { // >= accounts for NULL terminator
         return AVIF_APP_FILE_FORMAT_UNKNOWN;
     }

     for (size_t i = 0; i < fileExtLen; ++i) {
         lowercaseExt[i] = (char)tolower((unsigned char)fileExt[i]);
     }
     lowercaseExt[fileExtLen] = 0;

     if (!strcmp(lowercaseExt, "avif")) {
         return AVIF_APP_FILE_FORMAT_AVIF;
     } else if (!strcmp(lowercaseExt, "y4m")) {
         return AVIF_APP_FILE_FORMAT_Y4M;
     } else if (!strcmp(lowercaseExt, "jpg") || !strcmp(lowercaseExt, "jpeg")) {
         return AVIF_APP_FILE_FORMAT_JPEG;
     } else if (!strcmp(lowercaseExt, "png")) {
         return AVIF_APP_FILE_FORMAT_PNG;
     }
     return AVIF_APP_FILE_FORMAT_UNKNOWN;
 }

 avifAppFileFormat avifReadImage(const char * filename,
                                 avifPixelFormat requestedFormat,
                                 int requestedDepth,
                                 avifChromaDownsampling chromaDownsampling,
                                 avifBool ignoreColorProfile,
                                 avifBool ignoreExif,
                                 avifBool ignoreXMP,
                                 avifBool allowChangingCicp,
                                 avifImage * image,
                                 uint32_t * outDepth,
                                 avifAppSourceTiming * sourceTiming,
                                 struct y4mFrameIterator ** frameIter)
 {
     const avifAppFileFormat format = avifGuessFileFormat(filename);
     if (format == AVIF_APP_FILE_FORMAT_Y4M) {
         if (!y4mRead(filename, image, sourceTiming, frameIter)) {
             return AVIF_APP_FILE_FORMAT_UNKNOWN;
         }
         if (outDepth) {
             *outDepth = image->depth;
         }
     } else if (format == AVIF_APP_FILE_FORMAT_JPEG) {
         if (!avifJPEGRead(filename, image, requestedFormat, requestedDepth, chromaDownsampling, ignoreColorProfile, ignoreExif, ignoreXMP)) {
             return AVIF_APP_FILE_FORMAT_UNKNOWN;
         }
         if (outDepth) {
             *outDepth = 8;
         }
     } else if (format == AVIF_APP_FILE_FORMAT_PNG) {
         if (!avifPNGRead(filename, image, requestedFormat, requestedDepth, chromaDownsampling, ignoreColorProfile, ignoreExif, ignoreXMP, allowChangingCicp, outDepth)) {
             return AVIF_APP_FILE_FORMAT_UNKNOWN;
         }
     } else {
         fprintf(stderr, "Unrecognized file format for input file: %s\n", filename);
         return AVIF_APP_FILE_FORMAT_UNKNOWN;
     }
     return format;
 }

 void avifImageFixXMP(avifImage * image)
 {
     // Zero bytes are forbidden in UTF-8 XML: https://en.wikipedia.org/wiki/Valid_characters_in_XML
     // Keeping zero bytes in XMP may lead to issues at encoding or decoding.
     // For example, the PNG specification forbids null characters in XMP. See avifPNGWrite().
     // The XMP Specification Part 3 says "When XMP is encoded as UTF-8,
     // there are no zero bytes in the XMP packet" for GIF.

     // Consider a single trailing null character following a non-null character
     // as a programming error. Leave other null characters as is.
     // See the discussion at https://github.com/AOMediaCodec/libavif/issues/1333.
     if (image->xmp.size >= 2 && image->xmp.data[image->xmp.size - 1] == '\0' && image->xmp.data[image->xmp.size - 2] != '\0') {
         --image->xmp.size;
     }
 }

 void avifDumpDiagnostics(const avifDiagnostics * diag)
 {
     if (!*diag->error) {
         return;
     }

     printf("Diagnostics:\n");
     printf(" * %s\n", diag->error);
 }

 // ---------------------------------------------------------------------------
 // avifQueryCPUCount (separated into OS implementations)

 #if defined(_WIN32)

 // Windows

 #include <windows.h>

 int avifQueryCPUCount(void)
 {
     int numCPU;
     SYSTEM_INFO sysinfo;
     GetSystemInfo(&sysinfo);
     numCPU = sysinfo.dwNumberOfProcessors;
     return numCPU;
 }

 #elif defined(__APPLE__)

 // Apple

 #include <sys/sysctl.h>

 int avifQueryCPUCount()
 {
     int mib[4];
     int numCPU;
     size_t len = sizeof(numCPU);

     /* set the mib for hw.ncpu */
     mib[0] = CTL_HW;
     mib[1] = HW_AVAILCPU; // alternatively, try HW_NCPU;

     /* get the number of CPUs from the system */
     sysctl(mib, 2, &numCPU, &len, NULL, 0);

     if (numCPU < 1) {
         mib[1] = HW_NCPU;
         sysctl(mib, 2, &numCPU, &len, NULL, 0);
         if (numCPU < 1)
             numCPU = 1;
     }
     return numCPU;
 }

 #elif defined(__EMSCRIPTEN__)

 // Emscripten

 int avifQueryCPUCount()
 {
     return 1;
 }

 #else

 // POSIX

 #include <unistd.h>

 int avifQueryCPUCount()
 {
     int numCPU = (int)sysconf(_SC_NPROCESSORS_ONLN);
     return (numCPU > 0) ? numCPU : 1;
 }

 #endif
	// Copyright 2019 Joe Drago. All rights reserved.
	// SPDX-License-Identifier: BSD-2-Clause

	#include "avifutil.h"

	#include <ctype.h>
	#include <stdio.h>
	#include <string.h>

	#include "avifjpeg.h"
	#include "avifpng.h"
	#include "y4m.h"

	// \|a\| and \|b\| hold int32_t values. The int64_t type is used so that we can negate INT32_MIN without
	// overflowing int32_t.
	static int64_t calcGCD(int64_t a, int64_t b)
	{
	if (a < 0) {
	a *= -1;
	}
	if (b < 0) {
	b *= -1;
	}
	while (b != 0) {
	int64_t r = a % b;
	a = b;
	b = r;
	}
	return a;
	}

	static void printClapFraction(const char * name, int32_t n, int32_t d)
	{
	printf("%s: %d/%d", name, n, d);
	if (d != 0) {
	int64_t gcd = calcGCD(n, d);
	if (gcd > 1) {
	int32_t rn = (int32_t)(n / gcd);
	int32_t rd = (int32_t)(d / gcd);
	printf(" (%d/%d)", rn, rd);
	}
	}
	}

	static void avifImageDumpInternal(const avifImage * avif, uint32_t gridCols, uint32_t gridRows, avifBool alphaPresent, avifProgressiveState progressiveState)
	{
	uint32_t width = avif->width;
	uint32_t height = avif->height;
	if (gridCols && gridRows) {
	width *= gridCols;
	height *= gridRows;
	}
	printf(" * Resolution : %ux%u\n", width, height);
	printf(" * Bit Depth : %u\n", avif->depth);
	printf(" * Format : %s\n", avifPixelFormatToString(avif->yuvFormat));
	if (avif->yuvFormat == AVIF_PIXEL_FORMAT_YUV420) {
	printf(" * Chroma Sam. Pos: %u\n", avif->yuvChromaSamplePosition);
	}
	printf(" * Alpha : %s\n", alphaPresent ? (avif->alphaPremultiplied ? "Premultiplied" : "Not premultiplied") : "Absent");
	printf(" * Range : %s\n", (avif->yuvRange == AVIF_RANGE_FULL) ? "Full" : "Limited");

	printf(" * Color Primaries: %u\n", avif->colorPrimaries);
	printf(" * Transfer Char. : %u\n", avif->transferCharacteristics);
	printf(" * Matrix Coeffs. : %u\n", avif->matrixCoefficients);

	if (avif->icc.size != 0) {
	printf(" * ICC Profile : Present (%" AVIF_FMT_ZU " bytes)\n", avif->icc.size);
	} else {
	printf(" * ICC Profile : Absent\n");
	}
	if (avif->xmp.size != 0) {
	printf(" * XMP Metadata : Present (%" AVIF_FMT_ZU " bytes)\n", avif->xmp.size);
	} else {
	printf(" * XMP Metadata : Absent\n");
	}
	if (avif->exif.size != 0) {
	printf(" * Exif Metadata : Present (%" AVIF_FMT_ZU " bytes)\n", avif->exif.size);
	} else {
	printf(" * Exif Metadata : Absent\n");
	}

	if (avif->transformFlags == AVIF_TRANSFORM_NONE) {
	printf(" * Transformations: None\n");
	} else {
	printf(" * Transformations:\n");

	if (avif->transformFlags & AVIF_TRANSFORM_PASP) {
	printf(" * pasp (Aspect Ratio) : %d/%d\n", (int)avif->pasp.hSpacing, (int)avif->pasp.vSpacing);
	}
	if (avif->transformFlags & AVIF_TRANSFORM_CLAP) {
	printf(" * clap (Clean Aperture): ");
	printClapFraction("W", (int32_t)avif->clap.widthN, (int32_t)avif->clap.widthD);
	printf(", ");
	printClapFraction("H", (int32_t)avif->clap.heightN, (int32_t)avif->clap.heightD);
	printf(", ");
	printClapFraction("hOff", (int32_t)avif->clap.horizOffN, (int32_t)avif->clap.horizOffD);
	printf(", ");
	printClapFraction("vOff", (int32_t)avif->clap.vertOffN, (int32_t)avif->clap.vertOffD);
	printf("\n");

	avifCropRect cropRect;
	avifDiagnostics diag;
	avifDiagnosticsClearError(&diag);
	avifBool validClap =
	avifCropRectConvertCleanApertureBox(&cropRect, &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",
	cropRect.x,
	cropRect.y,
	cropRect.width,
	cropRect.height);
	} else {
	printf(" * Invalid: %s\n", diag.error);
	}
	}
	if (avif->transformFlags & AVIF_TRANSFORM_IROT) {
	printf(" * irot (Rotation) : %u\n", avif->irot.angle);
	}
	if (avif->transformFlags & AVIF_TRANSFORM_IMIR) {
	printf(" * imir (Mirror) : %u (%s)\n", avif->imir.axis, (avif->imir.axis == 0) ? "top-to-bottom" : "left-to-right");
	}
	}
	printf(" * Progressive : %s\n", avifProgressiveStateToString(progressiveState));
	if (avif->clli.maxCLL > 0 \|\| avif->clli.maxPALL > 0) {
	printf(" * CLLI : %hu, %hu\n", avif->clli.maxCLL, avif->clli.maxPALL);
	}
	}

	void avifImageDump(const avifImage * avif, uint32_t gridCols, uint32_t gridRows, avifProgressiveState progressiveState)
	{
	const avifBool alphaPresent = avif->alphaPlane && (avif->alphaRowBytes > 0);
	avifImageDumpInternal(avif, gridCols, gridRows, alphaPresent, progressiveState);
	}

	void avifContainerDump(const avifDecoder * decoder)
	{
	avifImageDumpInternal(decoder->image, 0, 0, decoder->alphaPresent, decoder->progressiveState);
	if ((decoder->progressiveState == AVIF_PROGRESSIVE_STATE_UNAVAILABLE) && (decoder->imageCount > 1)) {
	if (decoder->repetitionCount == AVIF_REPETITION_COUNT_INFINITE) {
	printf(" * Repeat Count : Infinite\n");
	} else if (decoder->repetitionCount == AVIF_REPETITION_COUNT_UNKNOWN) {
	printf(" * Repeat Count : Unknown\n");
	} else {
	printf(" * Repeat Count : %d\n", decoder->repetitionCount);
	}
	}
	}

	void avifPrintVersions(void)
	{
	char codecVersions[256];
	avifCodecVersions(codecVersions);
	printf("Version: %s (%s)\n", avifVersion(), codecVersions);

	unsigned int libyuvVersion = avifLibYUVVersion();
	if (libyuvVersion == 0) {
	printf("libyuv : unavailable\n");
	} else {
	printf("libyuv : available (%u)\n", libyuvVersion);
	}

	printf("\n");
	}

	avifAppFileFormat avifGuessFileFormat(const char * filename)
	{
	// Guess from the file header
	FILE * f = fopen(filename, "rb");
	if (f) {
	uint8_t headerBuffer[144];
	size_t bytesRead = fread(headerBuffer, 1, sizeof(headerBuffer), f);
	fclose(f);

	if (bytesRead > 0) {
	avifROData header;
	header.data = headerBuffer;
	header.size = bytesRead;

	if (avifPeekCompatibleFileType(&header)) {
	return AVIF_APP_FILE_FORMAT_AVIF;
	}

	static const uint8_t signatureJPEG[2] = { 0xFF, 0xD8 };
	static const uint8_t signaturePNG[8] = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
	static const uint8_t signatureY4M[9] = { 0x59, 0x55, 0x56, 0x34, 0x4D, 0x50, 0x45, 0x47, 0x32 }; // "YUV4MPEG2"
	struct avifHeaderSignature
	{
	avifAppFileFormat format;
	const uint8_t * magic;
	size_t magicSize;
	} signatures[] = { { AVIF_APP_FILE_FORMAT_JPEG, signatureJPEG, sizeof(signatureJPEG) },
	{ AVIF_APP_FILE_FORMAT_PNG, signaturePNG, sizeof(signaturePNG) },
	{ AVIF_APP_FILE_FORMAT_Y4M, signatureY4M, sizeof(signatureY4M) } };
	const size_t signaturesCount = sizeof(signatures) / sizeof(signatures[0]);

	for (size_t signatureIndex = 0; signatureIndex < signaturesCount; ++signatureIndex) {
	struct avifHeaderSignature * signature = &signatures[signatureIndex];
	if (header.size < signature->magicSize) {
	continue;
	}
	if (!memcmp(header.data, signature->magic, signature->magicSize)) {
	return signature->format;
	}
	}

	// If none of these signatures match, bail out here. Guessing by extension won't help.
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	}

	// If we get here, the file header couldn't be read for some reason. Guess from the extension.

	const char * fileExt = strrchr(filename, '.');
	if (!fileExt) {
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	++fileExt; // skip past the dot

	char lowercaseExt[8]; // This only needs to fit up to "jpeg", so this is plenty
	const size_t fileExtLen = strlen(fileExt);
	if (fileExtLen >= sizeof(lowercaseExt)) { // >= accounts for NULL terminator
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}

	for (size_t i = 0; i < fileExtLen; ++i) {
	lowercaseExt[i] = (char)tolower((unsigned char)fileExt[i]);
	}
	lowercaseExt[fileExtLen] = 0;

	if (!strcmp(lowercaseExt, "avif")) {
	return AVIF_APP_FILE_FORMAT_AVIF;
	} else if (!strcmp(lowercaseExt, "y4m")) {
	return AVIF_APP_FILE_FORMAT_Y4M;
	} else if (!strcmp(lowercaseExt, "jpg") \|\| !strcmp(lowercaseExt, "jpeg")) {
	return AVIF_APP_FILE_FORMAT_JPEG;
	} else if (!strcmp(lowercaseExt, "png")) {
	return AVIF_APP_FILE_FORMAT_PNG;
	}
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}

	avifAppFileFormat avifReadImage(const char * filename,
	avifPixelFormat requestedFormat,
	int requestedDepth,
	avifChromaDownsampling chromaDownsampling,
	avifBool ignoreColorProfile,
	avifBool ignoreExif,
	avifBool ignoreXMP,
	avifBool allowChangingCicp,
	avifImage * image,
	uint32_t * outDepth,
	avifAppSourceTiming * sourceTiming,
	struct y4mFrameIterator ** frameIter)
	{
	const avifAppFileFormat format = avifGuessFileFormat(filename);
	if (format == AVIF_APP_FILE_FORMAT_Y4M) {
	if (!y4mRead(filename, image, sourceTiming, frameIter)) {
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	if (outDepth) {
	*outDepth = image->depth;
	}
	} else if (format == AVIF_APP_FILE_FORMAT_JPEG) {
	if (!avifJPEGRead(filename, image, requestedFormat, requestedDepth, chromaDownsampling, ignoreColorProfile, ignoreExif, ignoreXMP)) {
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	if (outDepth) {
	*outDepth = 8;
	}
	} else if (format == AVIF_APP_FILE_FORMAT_PNG) {
	if (!avifPNGRead(filename, image, requestedFormat, requestedDepth, chromaDownsampling, ignoreColorProfile, ignoreExif, ignoreXMP, allowChangingCicp, outDepth)) {
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	} else {
	fprintf(stderr, "Unrecognized file format for input file: %s\n", filename);
	return AVIF_APP_FILE_FORMAT_UNKNOWN;
	}
	return format;
	}

	void avifImageFixXMP(avifImage * image)
	{
	// Zero bytes are forbidden in UTF-8 XML: https://en.wikipedia.org/wiki/Valid_characters_in_XML
	// Keeping zero bytes in XMP may lead to issues at encoding or decoding.
	// For example, the PNG specification forbids null characters in XMP. See avifPNGWrite().
	// The XMP Specification Part 3 says "When XMP is encoded as UTF-8,
	// there are no zero bytes in the XMP packet" for GIF.

	// Consider a single trailing null character following a non-null character
	// as a programming error. Leave other null characters as is.
	// See the discussion at https://github.com/AOMediaCodec/libavif/issues/1333.
	if (image->xmp.size >= 2 && image->xmp.data[image->xmp.size - 1] == '\0' && image->xmp.data[image->xmp.size - 2] != '\0') {
	--image->xmp.size;
	}
	}

	void avifDumpDiagnostics(const avifDiagnostics * diag)
	{
	if (!*diag->error) {
	return;
	}

	printf("Diagnostics:\n");
	printf(" * %s\n", diag->error);
	}

	// ---------------------------------------------------------------------------
	// avifQueryCPUCount (separated into OS implementations)

	#if defined(_WIN32)

	// Windows

	#include <windows.h>

	int avifQueryCPUCount(void)
	{
	int numCPU;
	SYSTEM_INFO sysinfo;
	GetSystemInfo(&sysinfo);
	numCPU = sysinfo.dwNumberOfProcessors;
	return numCPU;
	}

	#elif defined(__APPLE__)

	// Apple

	#include <sys/sysctl.h>

	int avifQueryCPUCount()
	{
	int mib[4];
	int numCPU;
	size_t len = sizeof(numCPU);

	/* set the mib for hw.ncpu */
	mib[0] = CTL_HW;
	mib[1] = HW_AVAILCPU; // alternatively, try HW_NCPU;

	/* get the number of CPUs from the system */
	sysctl(mib, 2, &numCPU, &len, NULL, 0);

	if (numCPU < 1) {
	mib[1] = HW_NCPU;
	sysctl(mib, 2, &numCPU, &len, NULL, 0);
	if (numCPU < 1)
	numCPU = 1;
	}
	return numCPU;
	}

	#elif defined(__EMSCRIPTEN__)

	// Emscripten

	int avifQueryCPUCount()
	{
	return 1;
	}

	#else

	// POSIX

	#include <unistd.h>

	int avifQueryCPUCount()
	{
	int numCPU = (int)sysconf(_SC_NPROCESSORS_ONLN);
	return (numCPU > 0) ? numCPU : 1;
	}

	#endif