// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* @fileoverview
* 'CrPngBehavior' is a behavior to convert image sequences into APNG
* (animated PNG) images.
*/
/**
* PNG frame delay fraction numerator.
* @const
*/
const PNG_FRAME_DELAY_NUMERATOR = 1;
/**
* PNG frame delay fraction denominator.
* @const
*/
const PNG_FRAME_DELAY_DENOMINATOR = 20;
/**
* PNG signature.
* @const
*/
const PNG_SIGNATURE = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
/**
* PNG bit depth (8 = 32bpp).
* @const
*/
const PNG_BIT_DEPTH = 8;
/**
* PNG compression method (0 = deflate/inflate compression with a sliding
* window PNG compression).
* @const
*/
const PNG_COMPRESSION_METHOD = 0;
/**
* PNG filter method (0 = adaptive filtering with five basic filter types).
* @const
*/
const PNG_FILTER_METHOD = 0;
/**
* PNG interlace method (0 = no interlace).
* @const
*/
const PNG_INTERLACE_METHOD = 0;
/**
* CRC table for PNG encode.
*
* Generated using:
*
* for (var i = 0; i < 256; i++) {
* var value = i;
* for (var j = 0; j < 8; j++) {
* if (value & 1)
* value = ((0xEDB88320) ^ (value >>> 1));
* else
* value = (value >>> 1);
* }
* TABLE[i] = value;
* }
*
* @const
*/
const PNG_CRC_TABLE = [
0x0, 0x77073096, 0xEE0E612C, 0x990951BA, 0x76DC419, 0x706AF48F,
0xE963A535, 0x9E6495A3, 0xEDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
0x9B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2,
0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C,
0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423,
0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190, 0x1DB7106,
0x98D220BC, 0xEFD5102A, 0x71B18589, 0x6B6B51F, 0x9FBFE4A5, 0xE8B8D433,
0x7807C9A2, 0xF00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x86D3D2D,
0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7,
0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA,
0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81,
0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6, 0x3B6E20C, 0x74B1D29A,
0xEAD54739, 0x9DD277AF, 0x4DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84,
0xD6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0xA00AE27, 0x7D079EB1,
0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E,
0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55,
0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28,
0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x26D930A, 0x9C0906A9, 0xEB0E363F,
0x72076785, 0x5005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0xCB61B38,
0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0xBDBDF21, 0x86D3D2D4, 0xF1D4E242,
0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69,
0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC,
0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693,
0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
];
/**
* PNG object state.
* @typedef {{
* frames: number,
* sequences: number,
* width: number,
* height: number,
* colour: number,
* chunks: !Array<Uint8Array>
* }}
*/
let CrPngState;
/**
* Construct an internal representation of the png.
* @param {!Array<string>} images The data URLs for each image.
* @return {!CrPngState}
* @private
*/
function convertDataUrlsToCrPng(images) {
const png =
/** @type {!CrPngState} */ ({frames: 0, sequences: 0, chunks: []});
/** Append signature. */
png.chunks.push(new Uint8Array(PNG_SIGNATURE));
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IHDR
*
* Width 4 bytes
* Height 4 bytes
* Bit depth 1 byte
* Colour type 1 byte
* Compression method 1 byte
* Filter method 1 byte
* Interlace method 1 byte
*/
const IHDR = new Uint8Array(12 + 13);
writeUInt32(IHDR, 13, 0);
writeFourCC(IHDR, 'IHDR', 4);
/** Write size at the end when known. */
writeUInt8(IHDR, PNG_BIT_DEPTH, 16);
/** Write colour at the end when known. */
writeUInt8(IHDR, PNG_COMPRESSION_METHOD, 18);
writeUInt8(IHDR, PNG_FILTER_METHOD, 19);
writeUInt8(IHDR, PNG_INTERLACE_METHOD, 20);
/** Write CRC at the end when size and colour is known. */
png.chunks.push(IHDR);
/**
* acTL
*
* Number of frames 4 bytes
* Number of times to loop 4 bytes
*/
const acTL = new Uint8Array(12 + 8);
writeUInt32(acTL, 8, 0);
writeFourCC(acTL, 'acTL', 4);
writeUInt32(acTL, images.length, 8);
writeUInt32(acTL, 0, 12);
writeUInt32(acTL, getCRC(acTL, 4, 16), 16);
png.chunks.push(acTL);
/** Append each image as a PNG frame. */
for (let i = 0; i < images.length; ++i) {
appendFrameFromDataURL(images[i], png);
}
/** Update IHDR now that size and colour is known. */
writeUInt32(IHDR, png.width, 8);
writeUInt32(IHDR, png.height, 12);
writeUInt8(IHDR, png.colour, 17);
writeUInt32(IHDR, getCRC(IHDR, 4, 8 + 13), 8 + 13);
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IEND
*/
const IEND = new Uint8Array(12);
writeUInt32(IEND, 0, 0);
writeFourCC(IEND, 'IEND', 4);
writeUInt32(IEND, getCRC(IEND, 4, 8), 8);
png.chunks.push(IEND);
return png;
}
/**
* Get a binary representation of the png.
* @param {!Array<string>} images The data URLs for each image.
* @return {!Uint8Array} Binary data for animated png image.
*/
export function convertImageSequenceToPngBinary(images) {
const png = convertDataUrlsToCrPng(images);
const numBytes =
png.chunks.reduce((value, next) => value + next.byteLength, 0);
const result = new Uint8Array(numBytes);
let offset = 0;
for (const chunk of png.chunks) {
result.set(/** @type {!ArrayBufferView} */ (chunk), offset);
offset += chunk.byteLength;
}
return result;
}
/**
* Returns a data URL for an animated PNG image that is created
* from a sequence of images.
* @param {!Array<string>} images The data URLs for each image.
* @return {string} A data URL for an animated PNG image.
*/
export function convertImageSequenceToPng(images) {
const png = convertDataUrlsToCrPng(images);
return 'data:image/png;base64,' +
btoa(png.chunks
.map(function(chunk) {
return String.fromCharCode.apply(null, chunk);
})
.join(''));
}
/**
* Returns true if the data URL is an animated PNG image. If the PNG is
* animated, then 'acTL' will have been set by convertImageSequenceToPng().
* acTL is the animation control chunk in the data stream of an animated PNG.
* If it exists we assume the image is animated, regardless of the number of
* frames. The offset is the PNG signature ( 8 bytes) + IHDR (25 bytes) + 4
* bytes of padding zeros. See https://wiki.mozilla.org/APNG_Specification
* @param {string} url An btoa encoded data URL for a PNG image.
* @return {boolean} True if data URL is an animated PNG image.
*/
export function isEncodedPngDataUrlAnimated(url) {
const decoded = atob(url.substr('data:image/png;base64,'.length));
return decoded.substr(37, 4) === 'acTL';
}
/**
* Reads Uint32 from buffer.
* @param {!Uint8Array} buffer Buffer to read UInt32 from.
* @param {number} offset Offset in buffer to read UInt32 at.
* @return {number} The value read.
*/
function readUInt32(buffer, offset) {
return (buffer[offset + 0] << 24) + (buffer[offset + 1] << 16) +
(buffer[offset + 2] << 8) + (buffer[offset + 3] << 0);
}
/**
* Reads string from buffer.
* @param {!Uint8Array} buffer Buffer to read string from.
* @param {number} offset Offset in buffer to read string at.
* @param {number} length Length of string to read.
* @return {string} The value read.
*/
function readString(buffer, offset, length) {
let str = '';
for (let i = 0; i < length; i++) {
str += String.fromCharCode(buffer[offset + i]);
}
return str;
}
/**
* Write bytes to buffer.
* @param {!Uint8Array} buffer Buffer to write bytes to.
* @param {!Uint8Array} bytes Array of bytes to be written.
* @param {number} offset Offset in buffer to write bytes at.
*/
function writeBytes(buffer, bytes, offset) {
for (let i = 0; i < bytes.length; i++) {
buffer[offset + i] = bytes[i] & 0xFF;
}
}
/**
* Write UInt8 to buffer.
* @param {!Uint8Array} buffer Buffer to write UInt8 to.
* @param {number} u8 UInt8 to be written.
* @param {number} offset Offset in buffer to write UInt8 at.
*/
function writeUInt8(buffer, u8, offset) {
buffer[offset] = u8 & 0xFF;
}
/**
* Write UInt16 to buffer.
* @param {!Uint8Array} buffer Buffer to write UInt16 to.
* @param {number} u16 UInt16 to be written.
* @param {number} offset Offset in buffer to write UInt16 at.
*/
function writeUInt16(buffer, u16, offset) {
buffer[offset + 0] = (u16 >> 8) & 0xFF;
buffer[offset + 1] = (u16 >> 0) & 0xFF;
}
/**
* Write UInt32 to buffer.
* @param {!Uint8Array} buffer Buffer to write UInt32 to.
* @param {number} u32 UInt32 to be written.
* @param {number} offset Offset in buffer to write UInt32 at.
*/
function writeUInt32(buffer, u32, offset) {
buffer[offset + 0] = (u32 >> 24) & 0xFF;
buffer[offset + 1] = (u32 >> 16) & 0xFF;
buffer[offset + 2] = (u32 >> 8) & 0xFF;
buffer[offset + 3] = (u32 >> 0) & 0xFF;
}
/**
* Write string to buffer.
* @param {!Uint8Array} buffer Buffer to write string to.
* @param {string} string String to be written.
* @param {number} offset Offset in buffer to write string at.
*/
function writeString(buffer, string, offset) {
for (let i = 0; i < string.length; i++) {
buffer[offset + i] = string.charCodeAt(i);
}
}
/**
* Write FourCC code to buffer.
* @param {!Uint8Array} buffer Buffer to write FourCC code to.
* @param {string} fourcc FourCC code to be written.
* @param {number} offset Offset in buffer to write FourCC code at.
*/
function writeFourCC(buffer, fourcc, offset) {
buffer[offset + 0] = fourcc.charCodeAt(0);
buffer[offset + 1] = fourcc.charCodeAt(1);
buffer[offset + 2] = fourcc.charCodeAt(2);
buffer[offset + 3] = fourcc.charCodeAt(3);
}
/**
* Compute CRC from buffer data.
* @param {!Uint8Array} buffer Buffer with data to compute CRC from.
* @param {number} start Start index in buffer.
* @param {number} end End index in buffer.
* @return {number} The computed CRC.
*/
function getCRC(buffer, start, end) {
let crc = 0xFFFFFFFF;
for (let i = start; i < end; i++) {
const crcTableIndex = (crc ^ (buffer[i])) & 0xFF;
crc = PNG_CRC_TABLE[crcTableIndex] ^ (crc >>> 8);
}
return crc ^ 0xFFFFFFFF;
}
/**
* Append frame from data URL to PNG object.
* @param {string} dataURL Data URL for frame.
* @param {!CrPngState} png PNG object to add frame to.
*/
function appendFrameFromDataURL(dataURL, png) {
/** Convert data URL to Uint8Array. */
const byteString = atob(dataURL.split(',')[1]);
const bytes = new Uint8Array(byteString.length);
writeString(bytes, byteString, 0);
/** Check signature. */
const signature = bytes.subarray(0, PNG_SIGNATURE.length);
if (signature.toString() !== PNG_SIGNATURE.toString()) {
console.error('Bad PNG signature');
}
/**
* fcTL
*
* Sequence number 4 bytes
* Width 4 bytes
* Height 4 bytes
* X position 4 bytes
* Y position 4 bytes
* Frame delay numerator 2 bytes
* Frame delay denominator 2 bytes
* Dispose op 1 bytes
* Blend op 1 bytes
*/
const fcTL = new Uint8Array(12 + 26);
writeUInt32(fcTL, 26, 0);
writeFourCC(fcTL, 'fcTL', 4);
writeUInt32(fcTL, png.sequences, 8);
/** Write size at the end when known. */
writeUInt32(fcTL, 0, 20);
writeUInt32(fcTL, 0, 24);
writeUInt16(fcTL, PNG_FRAME_DELAY_NUMERATOR, 28);
writeUInt16(fcTL, PNG_FRAME_DELAY_DENOMINATOR, 30);
writeUInt8(fcTL, 0, 32);
writeUInt8(fcTL, 0, 33);
/** Write CRC at the end when size is known. */
png.sequences += 1;
png.chunks.push(fcTL);
/** Append data chunks for frame. */
let i = PNG_SIGNATURE.length;
while ((i + 12) <= bytes.length) {
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#5Chunk-layout
*
* length = 4 bytes
* type = 4 bytes (IHDR, PLTE, IDAT, IEND or others)
* chunk = length bytes
* crc = 4 bytes
*/
const length = readUInt32(bytes, i);
const type = readString(bytes, i + 4, 4);
const chunk = bytes.subarray(i + 8, i + 8 + length);
/** We should have enough bytes left for length. */
if (length !== chunk.length) {
console.error('Unexpectedly reached end of file');
}
switch (type) {
case 'IHDR':
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IHDR
*
* Width 4 bytes
* Height 4 bytes
* Bit depth 1 byte
* Colour type 1 byte
* Compression method 1 byte
* Filter method 1 byte
* Interlace method 1 byte
*/
const width = readUInt32(chunk, 0);
const height = readUInt32(chunk, 4);
const depth = chunk[8];
const colour = chunk[9];
const compression = chunk[10];
const filter = chunk[11];
const interlace = chunk[12];
/** Initialize size and colour if this is the first frame. */
if (png.frames === 0) {
png.width = width;
png.height = height;
png.colour = colour;
}
/** Check that header matches our expectations. */
if (width !== png.width) {
console.error('Bad PNG width: ' + width);
}
if (height !== png.height) {
console.error('Bad PNG height: ' + height);
}
if (depth !== PNG_BIT_DEPTH) {
console.error('Bad PNG bit depth: ' + depth);
}
if (colour !== png.colour) {
console.error('Bad PNG colour type: ' + colour);
}
if (compression !== PNG_COMPRESSION_METHOD) {
console.error('Bad PNG compression method: ' + compression);
}
if (filter !== PNG_FILTER_METHOD) {
console.error('Bad PNG filter method: ' + filter);
}
if (interlace !== PNG_INTERLACE_METHOD) {
console.error('Bad PNG interlace method: ' + interlace);
}
break;
case 'IDAT':
/** Append as IDAT chunk if this is the first frame. */
if (png.frames === 0) {
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IDAT
*
* Data X bytes
*/
const IDAT = new Uint8Array(12 + length);
writeUInt32(IDAT, length, 0);
writeFourCC(IDAT, 'IDAT', 4);
writeBytes(IDAT, chunk, 8);
writeUInt32(IDAT, getCRC(IDAT, 4, 8 + length), 8 + length);
png.chunks.push(IDAT);
} else {
/**
* fdAT
*
* Sequence number 4 bytes
* Frame data X bytes
*/
const fdAT = new Uint8Array(12 + 4 + length);
writeUInt32(fdAT, 4 + length, 0);
writeFourCC(fdAT, 'fdAT', 4);
writeUInt32(fdAT, png.sequences, 8);
writeBytes(fdAT, chunk, 12);
writeUInt32(fdAT, getCRC(fdAT, 4, 12 + length), 12 + length);
png.sequences += 1;
png.chunks.push(fdAT);
}
break;
case 'PLTE':
/**
* https://www.w3.org/TR/2003/REC-PNG-20031110/#11PLTE
*
* Palette data X bytes
*/
const PLTE = new Uint8Array(12 + length);
writeUInt32(PLTE, length, 0);
writeFourCC(PLTE, 'PLTE', 4);
writeBytes(PLTE, chunk, 8);
writeUInt32(PLTE, getCRC(PLTE, 4, 8 + length), 8 + length);
png.chunks.push(PLTE);
break;
case 'IEND':
/** Update fcTL now that size is known. */
writeUInt32(fcTL, png.width, 12);
writeUInt32(fcTL, png.height, 16);
writeUInt32(fcTL, getCRC(fcTL, 4, 34), 34);
png.frames += 1;
return;
}
/** Advance to next chunk. */
i += 12 + length;
}
console.error('Unexpectedly reached end of file');
}
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