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https://github.com/bulwarkmail/webmail.git
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Linus Rath
f7a7828bfa
The host reads the size a PNG, GIF, JPEG, WebP or BMP declares in its header first: over 50 megapixels it answers too_big, trackers and tiny images are never decoded, a format whose header it can't read is unsupported, and large images are decoded at the target width. A browser that throws a TypeError on createImageBitmap's options decodes without them. The tests' stand-in pictures are now PNG headers instead of JSON (the code reads the header), so image-shrink.test.ts and plugin-host-attachment-image.test.ts build them that way, and the first shrink test expects the resize options on createImageBitmap.
67 lines
3.1 KiB
TypeScript
67 lines
3.1 KiB
TypeScript
// The width and height an image file declares in its header, read before
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// anything decodes it: PNG (IHDR), GIF, JPEG (the SOF segment), WebP
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// (VP8, VP8L, VP8X) and BMP. A file can declare a size whose pixels alone
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// would fill the memory, so callers check this first.
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export interface ImageDimensions {
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width: number;
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height: number;
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}
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/** Bytes of a file's start that hold the size of every format read here, EXIF blocks before a JPEG's SOF included. */
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export const IMAGE_HEADER_BYTES = 512 * 1024;
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const u16be = (b: Uint8Array, at: number) => (b[at] << 8) | b[at + 1];
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const u16le = (b: Uint8Array, at: number) => b[at] | (b[at + 1] << 8);
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const u24le = (b: Uint8Array, at: number) => b[at] | (b[at + 1] << 8) | (b[at + 2] << 16);
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const u32be = (b: Uint8Array, at: number) => ((b[at] << 24) >>> 0) + ((b[at + 1] << 16) | (b[at + 2] << 8) | b[at + 3]);
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const ascii = (b: Uint8Array, at: number, text: string) => [...text].every((c, i) => b[at + i] === c.charCodeAt(0));
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function jpeg(b: Uint8Array): ImageDimensions | null {
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let at = 2;
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while (at + 9 < b.length) {
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if (b[at] !== 0xff) return null;
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const marker = b[at + 1];
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// Fill bytes, and markers without a length (restart markers, TEM).
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if (marker === 0xff) { at++; continue; }
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if ((marker >= 0xd0 && marker <= 0xd7) || marker === 0x01) { at += 2; continue; }
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if (marker === 0xd9 || marker === 0xda) return null;
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const length = u16be(b, at + 2);
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// Start of frame: every SOF but DHT (C4), JPG (C8) and DAC (CC).
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if (marker >= 0xc0 && marker <= 0xcf && marker !== 0xc4 && marker !== 0xc8 && marker !== 0xcc) {
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return { height: u16be(b, at + 5), width: u16be(b, at + 7) };
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}
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if (length < 2) return null;
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at += 2 + length;
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}
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return null;
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}
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function webp(b: Uint8Array): ImageDimensions | null {
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if (b.length >= 30 && ascii(b, 12, 'VP8 ') && b[23] === 0x9d && b[24] === 0x01 && b[25] === 0x2a) {
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return { width: u16le(b, 26) & 0x3fff, height: u16le(b, 28) & 0x3fff };
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}
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if (ascii(b, 12, 'VP8L') && b[20] === 0x2f) {
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return {
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width: 1 + (((b[22] & 0x3f) << 8) | b[21]),
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height: 1 + (((b[24] & 0x0f) << 10) | (b[23] << 2) | ((b[22] & 0xc0) >> 6)),
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};
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}
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if (b.length >= 30 && ascii(b, 12, 'VP8X')) return { width: 1 + u24le(b, 24), height: 1 + u24le(b, 27) };
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return null;
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}
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/** The size the file declares, or null for a format not read here (or a damaged header). */
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export function imageDimensions(bytes: Uint8Array): ImageDimensions | null {
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const b = bytes;
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if (b.length >= 24 && b[0] === 0x89 && ascii(b, 1, 'PNG') && ascii(b, 12, 'IHDR')) return { width: u32be(b, 16), height: u32be(b, 20) };
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if (b.length >= 10 && ascii(b, 0, 'GIF8')) return { width: u16le(b, 6), height: u16le(b, 8) };
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if (b.length >= 4 && b[0] === 0xff && b[1] === 0xd8) return jpeg(b);
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if (b.length >= 25 && ascii(b, 0, 'RIFF') && ascii(b, 8, 'WEBP')) return webp(b);
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if (b.length >= 26 && ascii(b, 0, 'BM')) {
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const view = new DataView(b.buffer, b.byteOffset, b.byteLength);
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return { width: Math.abs(view.getInt32(18, true)), height: Math.abs(view.getInt32(22, true)) };
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}
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return null;
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}
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