Add comments and sanity checks to parsing of ICC headers
BUG=skia: GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1922073003 Review URL: https://codereview.chromium.org/1922073003
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@ -182,10 +182,18 @@ static uint16_t read_big_endian_short(const uint8_t* ptr) {
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return ptr[0] << 8 | ptr[1];
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}
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static uint32_t read_big_endian_int(const uint8_t* ptr) {
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static uint32_t read_big_endian_uint(const uint8_t* ptr) {
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return ptr[0] << 24 | ptr[1] << 16 | ptr[2] << 8 | ptr[3];
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}
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static int32_t read_big_endian_int(const uint8_t* ptr) {
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return (int32_t) read_big_endian_uint(ptr);
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}
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static bool color_space_almost_equal(float a, float b) {
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return SkTAbs(a - b) < 0.01f;
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}
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// This is equal to the header size according to the ICC specification (128)
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// plus the size of the tag count (4). We include the tag count since we
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// always require it to be present anyway.
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@ -195,29 +203,51 @@ static const size_t kICCHeaderSize = 132;
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static const size_t kICCTagTableEntrySize = 12;
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static const uint32_t kRGB_ColorSpace = SkSetFourByteTag('R', 'G', 'B', ' ');
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static const uint32_t kGray_ColorSpace = SkSetFourByteTag('G', 'R', 'A', 'Y');
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struct ICCProfileHeader {
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// TODO (msarett):
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// Can we ignore less of these fields?
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uint32_t fSize;
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// No reason to care about the preferred color management module (ex: Adobe, Apple, etc.).
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// We're always going to use this one.
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uint32_t fCMMType_ignored;
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uint32_t fVersion;
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uint32_t fClassProfile;
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uint32_t fColorSpace;
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uint32_t fProfileClass;
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uint32_t fInputColorSpace;
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uint32_t fPCS;
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uint32_t fDateTime_ignored[3];
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uint32_t fSignature;
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// Indicates the platform that this profile was created for (ex: Apple, Microsoft). This
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// doesn't really matter to us.
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uint32_t fPlatformTarget_ignored;
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// Flags can indicate:
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// (1) Whether this profile was embedded in a file. This flag is consistently wrong.
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// Ex: The profile came from a file but indicates that it did not.
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// (2) Whether we are allowed to use the profile independently of the color data. If set,
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// this may allow us to use the embedded profile for testing separate from the original
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// image.
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uint32_t fFlags_ignored;
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uint32_t fManufacturer_ignored;
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// We support many output devices. It doesn't make sense to think about the attributes of
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// the device in the context of the image profile.
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uint32_t fDeviceManufacturer_ignored;
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uint32_t fDeviceModel_ignored;
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uint32_t fDeviceAttributes_ignored[2];
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uint32_t fRenderingIntent;
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uint32_t fIlluminantXYZ_ignored[3];
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int32_t fIlluminantXYZ[3];
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// We don't care who created the profile.
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uint32_t fCreator_ignored;
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// This is an MD5 checksum. Could be useful for checking if profiles are equal.
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uint32_t fProfileId_ignored[4];
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// Reserved for future use.
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uint32_t fReserved_ignored[7];
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uint32_t fTagCount;
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void init(const uint8_t* src, size_t len) {
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@ -225,38 +255,34 @@ struct ICCProfileHeader {
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uint32_t* dst = (uint32_t*) this;
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for (uint32_t i = 0; i < kICCHeaderSize / 4; i++, src+=4) {
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dst[i] = read_big_endian_int(src);
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dst[i] = read_big_endian_uint(src);
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}
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}
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bool valid() const {
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// TODO (msarett):
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// For now it's nice to fail loudly on invalid inputs. But, can we
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// recover from some of these errors?
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return_if_false(fSize >= kICCHeaderSize, "Size is too small");
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uint8_t majorVersion = fVersion >> 24;
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return_if_false(majorVersion <= 4, "Unsupported version");
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// These are the three basic classes of profiles that we might expect to see embedded
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// in images. Four additional classes exist, but they generally are used as a convenient
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// way for CMMs to store calculated transforms.
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const uint32_t kDisplay_Profile = SkSetFourByteTag('m', 'n', 't', 'r');
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const uint32_t kInput_Profile = SkSetFourByteTag('s', 'c', 'n', 'r');
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const uint32_t kOutput_Profile = SkSetFourByteTag('p', 'r', 't', 'r');
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// TODO (msarett):
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// Should we also support DeviceLink, ColorSpace, Abstract, or NamedColor?
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return_if_false(fClassProfile == kDisplay_Profile ||
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fClassProfile == kInput_Profile ||
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fClassProfile == kOutput_Profile,
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"Unsupported class profile");
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return_if_false(fProfileClass == kDisplay_Profile ||
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fProfileClass == kInput_Profile ||
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fProfileClass == kOutput_Profile,
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"Unsupported profile");
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// TODO (msarett):
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// There are many more color spaces that we could try to support.
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return_if_false(fColorSpace == kRGB_ColorSpace || fColorSpace == kGray_ColorSpace,
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"Unsupported color space");
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// All the profiles we've tested so far use RGB as the input color space.
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return_if_false(fInputColorSpace == kRGB_ColorSpace, "Unsupported color space");
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// TODO (msarett):
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// All the profiles we've tested so far use XYZ as the profile connection space.
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const uint32_t kXYZ_PCSSpace = SkSetFourByteTag('X', 'Y', 'Z', ' ');
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// TODO (msarett):
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// Can we support PCS LAB as well?
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return_if_false(fPCS == kXYZ_PCSSpace, "Unsupported PCS space");
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return_if_false(fSignature == SkSetFourByteTag('a', 'c', 's', 'p'), "Bad signature");
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@ -267,6 +293,11 @@ struct ICCProfileHeader {
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// kSaturation (2), and kAbsolute (3).
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return_if_false(fRenderingIntent <= 3, "Bad rendering intent");
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return_if_false(color_space_almost_equal(SkFixedToFloat(fIlluminantXYZ[0]), 0.96420f) &&
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color_space_almost_equal(SkFixedToFloat(fIlluminantXYZ[1]), 1.00000f) &&
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color_space_almost_equal(SkFixedToFloat(fIlluminantXYZ[2]), 0.82491f),
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"Illuminant must be D50");
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return_if_false(fTagCount <= 100, "Too many tags");
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return true;
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@ -279,9 +310,9 @@ struct ICCTag {
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uint32_t fLength;
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const uint8_t* init(const uint8_t* src) {
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fSignature = read_big_endian_int(src);
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fOffset = read_big_endian_int(src + 4);
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fLength = read_big_endian_int(src + 8);
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fSignature = read_big_endian_uint(src);
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fOffset = read_big_endian_uint(src + 4);
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fLength = read_big_endian_uint(src + 8);
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return src + 12;
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}
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@ -335,7 +366,7 @@ static bool load_gamma(float* gamma, const uint8_t* src, size_t len) {
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return false;
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}
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uint32_t type = read_big_endian_int(src);
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uint32_t type = read_big_endian_uint(src);
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switch (type) {
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case kTAG_CurveType: {
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uint32_t count = read_big_endian_int(src + 8);
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@ -424,7 +455,7 @@ sk_sp<SkColorSpace> SkColorSpace::NewICC(const void* base, size_t len) {
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// Load our XYZ and gamma matrices.
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SkFloat3x3 toXYZ;
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SkFloat3 gamma {{ 1.0f, 1.0f, 1.0f }};
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switch (header.fColorSpace) {
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switch (header.fInputColorSpace) {
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case kRGB_ColorSpace: {
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const ICCTag* r = ICCTag::Find(tags.get(), tagCount, kTAG_rXYZ);
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const ICCTag* g = ICCTag::Find(tags.get(), tagCount, kTAG_gXYZ);
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