143 lines
4.0 KiB
TypeScript
143 lines
4.0 KiB
TypeScript
/**
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* Copyright (c) 2023 The xterm.js authors. All rights reserved.
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* @license MIT
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*/
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export type ImageType = 'image/png' | 'image/jpeg' | 'image/gif' | 'image/qoi' | 'image/webp' | 'image/avif' | 'unsupported' | '';
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export interface IMetrics {
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mime: ImageType;
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width: number;
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height: number;
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}
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export const UNSUPPORTED_TYPE: IMetrics = {
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mime: 'unsupported',
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width: 0,
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height: 0
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};
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export function imageType(d: Uint8Array): IMetrics {
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if (d.length < 32) {
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return UNSUPPORTED_TYPE;
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}
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const d32 = new Uint32Array(d.buffer, d.byteOffset, 8);
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// PNG: 89 50 4E 47 0D 0A 1A 0A (8 first bytes == magic number for PNG)
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// + first chunk must be IHDR
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if (d32[0] === 0x474E5089 && d32[1] === 0x0A1A0A0D && d32[3] === 0x52444849) {
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return {
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mime: 'image/png',
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width: d[16] << 24 | d[17] << 16 | d[18] << 8 | d[19],
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height: d[20] << 24 | d[21] << 16 | d[22] << 8 | d[23]
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};
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}
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// JPEG: FF D8 FF
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if (d[0] === 0xFF && d[1] === 0xD8 && d[2] === 0xFF) {
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const [width, height] = jpgSize(d);
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return { mime: 'image/jpeg', width, height };
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}
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// GIF: GIF87a or GIF89a
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if (d32[0] === 0x38464947 && (d[4] === 0x37 || d[4] === 0x39) && d[5] === 0x61) {
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return {
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mime: 'image/gif',
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width: d[7] << 8 | d[6],
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height: d[9] << 8 | d[8]
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};
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}
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// QOI: qoif
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if (d32[0] === 0x66696F71) {
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return {
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mime: 'image/qoi',
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width: d[4] << 24 | d[5] << 16 | d[6] << 8 | d[7],
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height: d[8] << 24 | d[9] << 16 | d[10] << 8 | d[11]
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};
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}
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// WEBP: RIFF | xxxx | WEBP | VP8x
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if (d32[0] === 0x46464952 && d32[2] === 0x50424557 && (d32[3] & 0xFFFFFF) === 0x385056) {
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switch (d[15]) {
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case 0x58: // Extended WebP VP8X --> "X"
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return {
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mime: 'image/webp',
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width: (d[24] | d[25] << 8 | d[26] << 16) + 1,
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height: (d[27] | d[28] << 8 | d[29] << 16) + 1
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};
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case 0x4C: // Lossless WebP VP8L --> "L"
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if (d[20] !== 0x2f) return UNSUPPORTED_TYPE;
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const dim = d[21] | d[22] << 8 | d[23] << 16 | d[24] << 24;
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return {
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mime: 'image/webp',
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width: (dim & 0x3FFF) + 1,
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height: (dim >>> 14 & 0x3FFF) + 1
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};
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case 0x20: // Lossy WebP VP8 --> " "
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if (d[23] !== 0x9d || d[24] !== 0x01 || d[25] !== 0x2a) return UNSUPPORTED_TYPE;
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return {
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mime: 'image/webp',
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width: (d[26] | d[27] << 8) & 0x3FFF,
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height: (d[28] | d[29] << 8) & 0x3FFF
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};
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}
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return UNSUPPORTED_TYPE;
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}
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// AVIF: Box size | ftyp | avif/avis
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if (d32[1] === 0x70797466 && (d32[2] === 0x66697661 || d32[2] === 0x73697661)) {
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let pos = -1;
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// search for ispe box within first 1024 bytes
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const limit = Math.min(d.length - 16, 1024);
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for (let i = 8; i < limit; i++) {
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// scan for ispe
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if (d[i] === 0x69 && d[i + 1] === 0x73 && d[i + 2] === 0x70 && d[i + 3] === 0x65) {
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pos = i;
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break;
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}
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}
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if (pos !== -1) {
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// dimensions are in BE at +8 (width) at +12 (height)
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const width =
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d[pos + 8] << 24 |
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d[pos + 9] << 16 |
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d[pos + 10] << 8 |
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d[pos + 11];
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const height =
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d[pos + 12] << 24 |
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d[pos + 13] << 16 |
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d[pos + 14] << 8 |
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d[pos + 15];
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if (width > 0 && height > 0) {
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return { mime: 'image/avif', width, height };
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}
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}
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return UNSUPPORTED_TYPE;
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}
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return UNSUPPORTED_TYPE;
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}
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function jpgSize(d: Uint8Array): [number, number] {
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const len = d.length;
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let i = 4;
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let blockLength = d[i] << 8 | d[i + 1];
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while (true) {
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i += blockLength;
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if (i >= len) {
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// exhausted without size info
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return [0, 0];
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}
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if (d[i] !== 0xFF) {
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return [0, 0];
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}
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if (d[i + 1] === 0xC0 || d[i + 1] === 0xC2) {
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if (i + 8 < len) {
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return [
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d[i + 7] << 8 | d[i + 8],
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d[i + 5] << 8 | d[i + 6]
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];
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}
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return [0, 0];
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}
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i += 2;
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blockLength = d[i] << 8 | d[i + 1];
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}
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}
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