cwebp: add PNG metadata extraction
the values of XMP/EXIF/ICC are currently unused.
Change-Id: I39d78b9a179f2d36c9c8ea12776bfdf6d8d18663
diff --git a/examples/cwebp.c b/examples/cwebp.c
index 47a9c3b..4004a9a 100644
--- a/examples/cwebp.c
+++ b/examples/cwebp.c
@@ -327,7 +327,7 @@
// If no size specified, try to decode it as PNG/JPEG (as appropriate).
const InputFileFormat format = GetImageType(in_file);
if (format == PNG_) {
- ok = ReadPNG(in_file, pic, keep_alpha);
+ ok = ReadPNG(in_file, pic, keep_alpha, metadata);
} else if (format == JPEG_) {
ok = ReadJPEG(in_file, pic);
} else if (format == TIFF_) {
diff --git a/examples/pngdec.c b/examples/pngdec.c
index ff98473..a6b271c 100644
--- a/examples/pngdec.c
+++ b/examples/pngdec.c
@@ -21,15 +21,173 @@
#include <stdlib.h>
#include "webp/encode.h"
+#include "./metadata.h"
static void PNGAPI error_function(png_structp png, png_const_charp dummy) {
(void)dummy; // remove variable-unused warning
longjmp(png_jmpbuf(png), 1);
}
-int ReadPNG(FILE* in_file, WebPPicture* const pic, int keep_alpha) {
+// Converts the NULL terminated 'hexstring' which contains 2-byte character
+// representations of hex values to raw data.
+// 'hexstring' may contain values consisting of [A-F][a-f][0-9] in pairs,
+// e.g., 7af2..., separated by any number of newlines.
+// 'expected_length' is the anticipated processed size.
+// On success the raw buffer is returned with its length equivalent to
+// 'expected_length'. NULL is returned if the processed length is less than
+// 'expected_length' or any character aside from those above is encountered.
+// The returned buffer must be freed by the caller.
+static uint8_t* HexStringToBytes(const char* hexstring,
+ size_t expected_length) {
+ const char* src = hexstring;
+ size_t actual_length = 0;
+ uint8_t* const raw_data = (uint8_t*)malloc(expected_length);
+ uint8_t* dst;
+
+ if (raw_data == NULL) return NULL;
+
+ for (dst = raw_data; actual_length < expected_length && *src != '\0'; ++src) {
+ char* end;
+ char val[3];
+ if (*src == '\n') continue;
+ val[0] = *src++;
+ val[1] = *src;
+ val[2] = '\0';
+ *dst++ = (uint8_t)strtol(val, &end, 16);
+ if (end != val + 2) break;
+ ++actual_length;
+ }
+
+ if (actual_length != expected_length) {
+ free(raw_data);
+ return NULL;
+ }
+ return raw_data;
+}
+
+static int ProcessRawProfile(const char* profile, size_t profile_len,
+ MetadataPayload* const payload) {
+ const char* src = profile;
+ char* end;
+ int expected_length;
+
+ if (profile == NULL || profile_len == 0) return 0;
+
+ // ImageMagick formats 'raw profiles' as
+ // '\n<name>\n<length>(%8lu)\n<hex payload>\n'.
+ if (*src != '\n') {
+ fprintf(stderr, "Malformed raw profile, expected '\\n' got '\\x%.2X'\n",
+ *src);
+ return 0;
+ }
+ ++src;
+ // skip the profile name and extract the length.
+ while (*src != '\0' && *src++ != '\n') {}
+ expected_length = (int)strtol(src, &end, 10);
+ if (*end != '\n') {
+ fprintf(stderr, "Malformed raw profile, expected '\\n' got '\\x%.2X'\n",
+ *end);
+ return 0;
+ }
+ ++end;
+
+ // 'end' now points to the profile payload.
+ payload->bytes = HexStringToBytes(end, expected_length);
+ if (payload->bytes == NULL) return 0;
+ payload->size = expected_length;
+ return 1;
+}
+
+static const struct {
+ const char* name;
+ int (*process)(const char* profile, size_t profile_len,
+ MetadataPayload* const payload);
+ size_t storage_offset;
+} kPNGMetadataMap[] = {
+ // http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/PNG.html#TextualData
+ // See also: ExifTool on CPAN.
+ { "Raw profile type exif", ProcessRawProfile, METADATA_OFFSET(exif) },
+ { "Raw profile type xmp", ProcessRawProfile, METADATA_OFFSET(xmp) },
+ // XMP Specification Part 3, Section 3 #PNG
+ { "XML:com.adobe.xmp", MetadataCopy, METADATA_OFFSET(xmp) },
+ { NULL, NULL, 0 },
+};
+
+// Looks for metadata at both the beginning and end of the PNG file, giving
+// preference to the head.
+// Returns true on success. The caller must use MetadataFree() on 'metadata' in
+// all cases.
+static int ExtractMetadataFromPNG(png_structp png,
+ png_infop const head_info,
+ png_infop const end_info,
+ Metadata* const metadata) {
+ int p;
+
+ for (p = 0; p < 2; ++p) {
+ png_infop const info = (p == 0) ? head_info : end_info;
+ png_textp text = NULL;
+ const int num = png_get_text(png, info, &text, NULL);
+ int i;
+ // Look for EXIF / XMP metadata.
+ for (i = 0; i < num; ++i, ++text) {
+ int j;
+ for (j = 0; kPNGMetadataMap[j].name != NULL; ++j) {
+ if (!strcmp(text->key, kPNGMetadataMap[j].name)) {
+ MetadataPayload* const payload =
+ (MetadataPayload*)((uint8_t*)metadata +
+ kPNGMetadataMap[j].storage_offset);
+ png_size_t text_length;
+ switch (text->compression) {
+#ifdef PNG_iTXt_SUPPORTED
+ case PNG_ITXT_COMPRESSION_NONE:
+ case PNG_ITXT_COMPRESSION_zTXt:
+ text_length = text->itxt_length;
+ break;
+#endif
+ default:
+ case PNG_TEXT_COMPRESSION_NONE:
+ case PNG_TEXT_COMPRESSION_zTXt:
+ text_length = text->text_length;
+ break;
+ }
+ if (payload->bytes != NULL) {
+ fprintf(stderr, "Ignoring additional '%s'\n", text->key);
+ } else if (!kPNGMetadataMap[j].process(text->text, text_length,
+ payload)) {
+ fprintf(stderr, "Failed to process: '%s'\n", text->key);
+ return 0;
+ }
+ break;
+ }
+ }
+ }
+ // Look for an ICC profile.
+ {
+ png_charp name;
+ int comp_type;
+#if ((PNG_LIBPNG_VER_MAJOR << 8) | PNG_LIBPNG_VER_MINOR << 0) < \
+ ((1 << 8) | (5 << 0))
+ png_charp profile;
+#else // >= libpng 1.5.0
+ png_bytep profile;
+#endif
+ png_uint_32 len;
+
+ if (png_get_iCCP(png, info,
+ &name, &comp_type, &profile, &len) == PNG_INFO_iCCP) {
+ if (!MetadataCopy((const char*)profile, len, &metadata->iccp)) return 0;
+ }
+ }
+ }
+
+ return 1;
+}
+
+int ReadPNG(FILE* in_file, WebPPicture* const pic, int keep_alpha,
+ Metadata* const metadata) {
png_structp png;
- png_infop info;
+ png_infop info = NULL;
+ png_infop end_info = NULL;
int color_type, bit_depth, interlaced;
int has_alpha;
int num_passes;
@@ -47,13 +205,16 @@
png_set_error_fn(png, 0, error_function, NULL);
if (setjmp(png_jmpbuf(png))) {
Error:
- png_destroy_read_struct(&png, NULL, NULL);
+ MetadataFree(metadata);
+ png_destroy_read_struct(&png, &info, &end_info);
free(rgb);
goto End;
}
info = png_create_info_struct(png);
if (info == NULL) goto Error;
+ end_info = png_create_info_struct(png);
+ if (end_info == NULL) goto Error;
png_init_io(png, in_file);
png_read_info(png, info);
@@ -94,8 +255,15 @@
png_read_rows(png, &row, NULL, 1);
}
}
- png_read_end(png, info);
- png_destroy_read_struct(&png, &info, NULL);
+ png_read_end(png, end_info);
+
+ if (metadata != NULL &&
+ !ExtractMetadataFromPNG(png, info, end_info, metadata)) {
+ fprintf(stderr, "Error extracting PNG metadata!\n");
+ goto Error;
+ }
+
+ png_destroy_read_struct(&png, &info, &end_info);
pic->width = width;
pic->height = height;
@@ -103,7 +271,10 @@
: WebPPictureImportRGB(pic, rgb, stride);
free(rgb);
- if (ok && has_alpha && keep_alpha == 2) {
+ if (!ok) {
+ goto Error;
+ }
+ if (has_alpha && keep_alpha == 2) {
WebPCleanupTransparentArea(pic);
}
@@ -111,10 +282,12 @@
return ok;
}
#else // !WEBP_HAVE_PNG
-int ReadPNG(FILE* in_file, struct WebPPicture* const pic, int keep_alpha) {
+int ReadPNG(FILE* in_file, struct WebPPicture* const pic, int keep_alpha,
+ struct Metadata* const metadata) {
(void)in_file;
(void)pic;
(void)keep_alpha;
+ (void)metadata;
fprintf(stderr, "PNG support not compiled. Please install the libpng "
"development package before building.\n");
return 0;
diff --git a/examples/pngdec.h b/examples/pngdec.h
index 5cee3ad..f53f863 100644
--- a/examples/pngdec.h
+++ b/examples/pngdec.h
@@ -16,13 +16,15 @@
extern "C" {
#endif
+struct Metadata;
struct WebPPicture;
// Reads a PNG from 'in_file', returning the decoded output in 'pic'.
// If 'keep_alpha' is true and the PNG has an alpha channel, the output is RGBA
// otherwise it will be RGB.
// Returns true on success.
-int ReadPNG(FILE* in_file, struct WebPPicture* const pic, int keep_alpha);
+int ReadPNG(FILE* in_file, struct WebPPicture* const pic, int keep_alpha,
+ struct Metadata* const metadata);
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"