Extremely Popular
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224/* global SharedArrayBuffer */import {crc32} from './crc32.js';import {Buffer} from './buffer.js';import {compress, decompress} from './wasm/zlib.js';
const __IHDR__ = new Uint8Array([73, 72, 68, 82]);const __IDAT__ = new Uint8Array([73, 68, 65, 84]);const __IEND__ = new Uint8Array([73, 69, 78, 68]);const __IEND_CRC__ = crc32(new Uint8Array([73, 69, 78, 68]));const HEAD = new Uint8Array([137, 80, 78, 71, 13, 10, 26, 10]);
const color_types = { GREYSCALE: 0, TRUECOLOR: 2, INDEXED_COLOR: 3, GREYSCALE_ALPHA: 4, TRUECOLOR_ALPHA: 6};
const channels_to_color_type = { 1: color_types.GREYSCALE, 2: color_types.GREYSCALE_ALPHA,
3: color_types.TRUECOLOR, 4: color_types.TRUECOLOR_ALPHA};
export async function encode(data, {width, height, channels, depth = 8, level = 0}) { let offset = 0; let tmp_offset = 0; const row_length = width * channels; const tmp = new Uint8Array(height + data.length);
while (offset < data.length) { tmp[tmp_offset++] = 0; tmp.set(data.subarray(offset, (offset += row_length)), tmp_offset);
tmp_offset += row_length; }
const compressed = await compress(tmp, level); const array = new Uint8Array(49 + HEAD.length + compressed.length);
array[26] = 0; array[27] = 0; array[28] = 0; array[24] = depth; array.set(HEAD, 0); array.set(__IHDR__, 12); array.set(__IDAT__, 37); array.set(compressed, 41); array.set(__IEND__, 49 + compressed.length); array[25] = channels_to_color_type[channels];
const view = new DataView(array.buffer);
view.setUint32(8, 13); view.setUint32(16, width); view.setUint32(20, height); view.setUint32(33, compressed.length); view.setUint32(45 + compressed.length, 0); view.setUint32(53 + compressed.length, __IEND_CRC__); view.setUint32(29, crc32(new Uint8Array(array.buffer, 12, 17))); view.setUint32(41 + compressed.length, crc32(new Uint8Array(array.buffer, 37, 4 + compressed.length)));
return array;}
export async function decode(array) { let view = new DataView(array.buffer, array.byteOffset, array.byteLength);
const width = view.getUint32(16); const height = view.getUint32(20); const bpc = array[24]; const pixel_type = array[25]; let channels = ({3: 1, 0: 1, 4: 2, 2: 3, 6: 4})[pixel_type]; const bytespp = channels * bpc / 8;
const row_length = width * bytespp; let pixels = new Uint8Array(height * row_length);
let offset = 0; let p_offset = 0;
let c_offset = 33; const chunks = [];
let palette, alphaPalette; let type; while (type !== 1229278788) { type = view.getUint32(4 + c_offset);
// IDAT if (type === 1229209940) chunks.push(array.subarray(8 + c_offset, 8 + c_offset + view.getUint32(c_offset))); else if (type === 1347179589) { // PLTE if (palette) throw new Error('PLTE can only occur once in an image'); palette = new Uint32Array(view.getUint32(c_offset)); for (let pxlOffset = 0; pxlOffset < palette.length * 8; pxlOffset += 3) palette[pxlOffset / 3] = array[8 + c_offset + pxlOffset] << 24 | array[8 + c_offset + pxlOffset + 1] << 16 | array[8 + c_offset + pxlOffset + 2] << 8 | 0xff; } else if (type === 1951551059) { // tRNS if (alphaPalette) throw new Error('tRNS can only occur once in an image'); alphaPalette = new Uint8Array(view.getUint32(c_offset)); for (let i = 0; i < alphaPalette.length; i++) alphaPalette[i] = array[8 + c_offset + i]; }
c_offset += 4 + 4 + 4 + view.getUint32(c_offset); }
array = await decompress(chunks.length === 1 ? chunks[0] : Buffer.concat(...chunks));
while (offset < array.byteLength) { const filter = array[offset++]; const slice = array.subarray(offset, offset += row_length);
if (0 === filter) pixels.set(slice, p_offset); else if (1 === filter) filter_1(slice, pixels, p_offset, bytespp, row_length); else if (2 === filter) filter_2(slice, pixels, p_offset, bytespp, row_length); else if (3 === filter) filter_3(slice, pixels, p_offset, bytespp, row_length); else if (4 === filter) filter_4(slice, pixels, p_offset, bytespp, row_length);
p_offset += row_length; }
if (pixel_type === 3) { if (!palette) throw new Error('Indexed color PNG has no PLTE');
if (alphaPalette) for (let i = 0; i < alphaPalette.length; i++) palette[i] &= 0xffffff00 | alphaPalette[i];
channels = 4; const newPixels = new Uint8Array(width * height * 4); const pixelView = new DataView(newPixels.buffer, newPixels.byteOffset, newPixels.byteLength); for (let i = 0; i < pixels.length; i++) pixelView.setUint32(i * 4, palette[pixels[i]], false); pixels = newPixels; }
if (bpc !== 8) { const newPixels = new Uint8Array(pixels.length / bpc * 8); for (let i = 0; i < pixels.length; i += 2) newPixels[i / 2] = pixels[i]; pixels = newPixels; }
if (channels !== 4) { const newPixels = new Uint8Array(width * height * 4); const view = new DataView(newPixels.buffer);
if (channels === 1) { for (let i = 0; i < width * height; i++) { const pixel = pixels[i]; view.setUint32(i * 4, pixel << 24 | pixel << 16 | pixel << 8 | 0xff, false); } } else if (channels === 2) { for (let i = 0; i < width * height * 2; i += 2) { const pixel = pixels[i]; view.setUint32(i * 2, pixel << 24 | pixel << 16 | pixel << 8 | pixels[i + 1], false); } } else if (channels === 3) {newPixels.fill(0xff); for (let i = 0; i < width * height; i++) newPixels.set(pixels.subarray(i * 3, i * 3 + 3), i * 4);}
pixels = newPixels; }
return {width, height, pixels}; }
function filter_1(slice, pixels, p_offset, bytespp, row_length) { let i = 0; while (i < bytespp) pixels[i + p_offset] = slice[i++]; while (i < row_length) pixels[i + p_offset] = slice[i] + pixels[i++ + p_offset - bytespp];}
function filter_2(slice, pixels, p_offset, bytespp, row_length) { if (0 === p_offset) pixels.set(slice, p_offset); else { let i = 0; while (i < row_length) pixels[i + p_offset] = slice[i] + pixels[i++ + p_offset - row_length]; }}
function filter_3(slice, pixels, p_offset, bytespp, row_length) { let i = 0;
if (0 === p_offset) { while (i < bytespp) pixels[i] = slice[i++]; while (i < row_length) pixels[i] = slice[i] + (pixels[i++ - bytespp] >> 1); } else { while (i < bytespp) pixels[i + p_offset] = slice[i] + (pixels[i++ + p_offset - row_length] >> 1); while (i < row_length) pixels[i + p_offset] = slice[i] + (pixels[i + p_offset - bytespp] + pixels[i++ + p_offset - row_length] >> 1); }}
function filter_4(slice, pixels, p_offset, bytespp, row_length) { let i = 0;
if (0 === p_offset) { while (i < bytespp) pixels[i] = slice[i++]; while (i < row_length) pixels[i] = slice[i] + pixels[i++ - bytespp]; } else { while (i < bytespp) pixels[i + p_offset] = slice[i] + pixels[i++ + p_offset - row_length];
while (i < row_length) { const a = pixels[i + p_offset - bytespp]; const b = pixels[i + p_offset - row_length]; const c = pixels[i + p_offset - bytespp - row_length];
const p = a + b - c; const pa = Math.abs(p - a); const pb = Math.abs(p - b); const pc = Math.abs(p - c);
pixels[i + p_offset] = slice[i++] + ((pa <= pb && pa <= pc) ? a : ((pb <= pc) ? b : c)); } }}