Exemple #1
0
static bool is_orientation_marker(jpeg_marker_struct* marker, SkCodec::Origin* orientation) {
    if (kExifMarker != marker->marker || marker->data_length < kExifHeaderSize) {
        return false;
    }

    const uint8_t* data = marker->data;
    static const uint8_t kExifSig[] { 'E', 'x', 'i', 'f', '\0' };
    if (memcmp(data, kExifSig, sizeof(kExifSig))) {
        return false;
    }

    bool littleEndian;
    if (!is_valid_endian_marker(data + 6, &littleEndian)) {
        return false;
    }

    // Get the offset from the start of the marker.
    // Account for 'E', 'x', 'i', 'f', '\0', '<fill byte>'.
    uint32_t offset = get_endian_int(data + 10, littleEndian);
    offset += sizeof(kExifSig) + 1;

    // Require that the marker is at least large enough to contain the number of entries.
    if (marker->data_length < offset + 2) {
        return false;
    }
    uint32_t numEntries = get_endian_short(data + offset, littleEndian);

    // Tag (2 bytes), Datatype (2 bytes), Number of elements (4 bytes), Data (4 bytes)
    const uint32_t kEntrySize = 12;
    numEntries = SkTMin(numEntries, (marker->data_length - offset - 2) / kEntrySize);

    // Advance the data to the start of the entries.
    data += offset + 2;

    const uint16_t kOriginTag = 0x112;
    const uint16_t kOriginType = 3;
    for (uint32_t i = 0; i < numEntries; i++, data += kEntrySize) {
        uint16_t tag = get_endian_short(data, littleEndian);
        uint16_t type = get_endian_short(data + 2, littleEndian);
        uint32_t count = get_endian_int(data + 4, littleEndian);
        if (kOriginTag == tag && kOriginType == type && 1 == count) {
            uint16_t val = get_endian_short(data + 8, littleEndian);
            if (0 < val && val <= SkCodec::kLast_Origin) {
                *orientation = (SkCodec::Origin) val;
                return true;
            }
        }
    }

    return false;
}
Exemple #2
0
    // Quick check if the image contains a valid TIFF header as requested by DNG format.
    bool isTiffHeaderValid() const {
        const size_t kHeaderSize = 4;
        SkAutoSTMalloc<kHeaderSize, unsigned char> header(kHeaderSize);
        if (!fStream->read(header.get(), 0 /* offset */, kHeaderSize)) {
            return false;
        }

        // Check if the header is valid (endian info and magic number "42").
        bool littleEndian;
        if (!is_valid_endian_marker(header, &littleEndian)) {
            return false;
        }

        return 0x2A == get_endian_short(header + 2, littleEndian);
    }