JPEG decoder: Reading offsets from EXIF was off by two bytes.

For rational numbers this worked OK by chance when both the nominator and
the denominator were < 65536, because the error was cancelled by the
division. However, this doesn't work when the nominator/denominator are
larger than 65535.

Fixed the offset, and added a test with large nom/denom.

Bug: 1143645
Change-Id: Ic8e46c580437fb4585197807c89a48f43435852a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2507110Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822179}

third_party/blink/renderer/platform/image-decoders/jpeg/jpeg_image_decoder.cc

@@ -315,7 +315,7 @@ static void ReadExifDirectory(JOCTET* dir_start,
     kOrientationTag = 0x112,
     kResolutionXTag = 0x11a,
     kResolutionYTag = 0x11b,
-    kresolution_unitTag = 0x128,
+    kResolutionUnitTag = 0x128,
     kPixelXDimensionTag = 0xa002,
     kPixelYDimensionTag = 0xa003,
     kExifOffsetTag = 0x8769
@@ -353,7 +353,7 @@ static void ReadExifDirectory(JOCTET* dir_start,
           metadata.orientation = ImageOrientation::FromEXIFValue(ReadUint16(value_ptr, is_big_endian));
         break;
 
-      case ExifTags::kresolution_unitTag:
+      case ExifTags::kResolutionUnitTag:
         if (type == kUnsignedShortType && count == 1)
           metadata.resolution_unit = ReadUint16(value_ptr, is_big_endian);
         break;
@@ -431,7 +431,7 @@ static void ReadImageMetaData(jpeg_decompress_struct* info, DecodedImageMetaData
     // http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
     JOCTET* data_end = marker->data + marker->data_length;
     JOCTET* root_start = marker->data + kOffsetToTiffData;
-    JOCTET* tiff_start = marker->data + ifd_offset;
+    JOCTET* tiff_start = marker->data + ifd_offset - 2;
     JOCTET* ifd0 = root_start + ifd_offset;
 
     ReadExifDirectory(ifd0, tiff_start, root_start, data_end, is_big_endian, metadata);

third_party/blink/web_tests/external/wpt/density-size-correction/density-corrected-natural-size.html

@@ -23,6 +23,7 @@
         await test_valid({width: 10, height: 20, preferredWidth: 20, preferredHeight: 10, resolutionX: 36, resolutionY: 144, resolutionUnit: 2})
         await test_valid({width: 10, height: 20, preferredWidth: 10, preferredHeight: 40, resolutionX: 72, resolutionY: 36, resolutionUnit: 2})
         await test_valid({width: 30, height: 30, preferredWidth: 90, preferredHeight: 30, resolutionX: 24, resolutionY: 72, resolutionUnit: 2})
+        await test_valid({width: 10, height: 20, preferredWidth: 20, preferredHeight: 40, resolutionX: [72 * 1000000, 2 * 1000000], resolutionY: [72 * 10000000, 2 * 10000000], resolutionUnit: 2})
 
         await test_invalid({width: 10, height: 20, preferredWidth: 20, preferredHeight: 30, resolutionX: 36, resolutionY: 36, resolutionUnit: 2})
         await test_invalid({width: 10, height: 20, preferredWidth: 33, preferredHeight: 40, resolutionX: 36, resolutionY: 36, resolutionUnit: 2})

third_party/blink/web_tests/external/wpt/density-size-correction/resources/exify.js

@@ -20,9 +20,9 @@ function createImageWithMetadata({
     if (orientation !== undefined)
         root[piexif.ExifIFD.Orientation] = orientation
     if (resolutionX !== undefined)
-        root[piexif.ImageIFD.XResolution] = [resolutionX, 1]
+        root[piexif.ImageIFD.XResolution] = Array.isArray(resolutionX) ? resolutionX : [resolutionX, 1]
     if (resolutionY !== undefined)
-        root[piexif.ImageIFD.YResolution] = [resolutionY, 1]
+        root[piexif.ImageIFD.YResolution] = Array.isArray(resolutionY) ? resolutionY : [resolutionY, 1]
     if (resolutionUnit !== undefined)
         root[piexif.ImageIFD.ResolutionUnit] = resolutionUnit
     if (preferredWidth !== undefined)