@tldraw/utils/dist-esm/lib/media/gif.mjs.map

tldraw infinite canvas SDK (private utilities).

{
  "version": 3,
  "sources": ["../../../src/lib/media/gif.ts"],
  "sourcesContent": ["/*!\n * MIT License\n * Modified code originally from <https://github.com/qzb/is-animated>\n * Copyright (c) 2016 J\u00F3zef Soko\u0142owski <j.k.sokolowski@gmail.com>\n */\n\n/** Returns total length of data blocks sequence */\nfunction getDataBlocksLength(buffer: Uint8Array, offset: number): number {\n\tlet length = 0\n\n\twhile (buffer[offset + length]) {\n\t\tlength += buffer[offset + length] + 1\n\t}\n\n\treturn length + 1\n}\n\n/**\n * Checks if buffer contains GIF image by examining the file header.\n *\n * @param buffer - The ArrayBuffer containing the image data to check\n * @returns True if the buffer contains a GIF image, false otherwise\n * @example\n * ```ts\n * // Check a file from user input\n * const file = event.target.files[0]\n * const buffer = await file.arrayBuffer()\n * const isGif = isGIF(buffer)\n * console.log(isGif ? 'GIF image' : 'Not a GIF')\n * ```\n * @public\n */\nexport function isGIF(buffer: ArrayBuffer): boolean {\n\tconst enc = new TextDecoder('ascii')\n\tconst header = enc.decode(buffer.slice(0, 3))\n\treturn header === 'GIF'\n}\n\n/**\n * Checks if buffer contains animated GIF image by parsing the GIF structure and counting image descriptors.\n * A GIF is considered animated if it contains more than one image descriptor block.\n *\n * @param buffer - The ArrayBuffer containing the GIF image data\n * @returns True if the GIF is animated (contains multiple frames), false otherwise\n * @example\n * ```ts\n * // Check if a GIF file is animated\n * const file = event.target.files[0]\n * if (file.type === 'image/gif') {\n *   const buffer = await file.arrayBuffer()\n *   const animated = isGifAnimated(buffer)\n *   console.log(animated ? 'Animated GIF' : 'Static GIF')\n * }\n * ```\n * @public\n */\nexport function isGifAnimated(buffer: ArrayBuffer): boolean {\n\tconst view = new Uint8Array(buffer)\n\tlet hasColorTable, colorTableSize\n\tlet offset = 0\n\tlet imagesCount = 0\n\n\t// Check if this is this image has valid GIF header.\n\t// If not return false. Chrome, FF and IE doesn't handle GIFs with invalid version.\n\tif (!isGIF(buffer)) {\n\t\treturn false\n\t}\n\n\t// Skip header, logical screen descriptor and global color table\n\n\thasColorTable = view[10] & 0x80 // 0b10000000\n\tcolorTableSize = view[10] & 0x07 // 0b00000111\n\n\toffset += 6 // skip header\n\toffset += 7 // skip logical screen descriptor\n\toffset += hasColorTable ? 3 * Math.pow(2, colorTableSize + 1) : 0 // skip global color table\n\n\t// Find if there is more than one image descriptor\n\n\twhile (imagesCount < 2 && offset < view.length) {\n\t\tswitch (view[offset]) {\n\t\t\t// Image descriptor block. According to specification there could be any\n\t\t\t// number of these blocks (even zero). When there is more than one image\n\t\t\t// descriptor browsers will display animation (they shouldn't when there\n\t\t\t// is no delays defined, but they do it anyway).\n\t\t\tcase 0x2c:\n\t\t\t\timagesCount += 1\n\n\t\t\t\thasColorTable = view[offset + 9] & 0x80 // 0b10000000\n\t\t\t\tcolorTableSize = view[offset + 9] & 0x07 // 0b00000111\n\n\t\t\t\toffset += 10 // skip image descriptor\n\t\t\t\toffset += hasColorTable ? 3 * Math.pow(2, colorTableSize + 1) : 0 // skip local color table\n\t\t\t\toffset += getDataBlocksLength(view, offset + 1) + 1 // skip image data\n\n\t\t\t\tbreak\n\n\t\t\t// Skip all extension blocks. In theory this \"plain text extension\" blocks\n\t\t\t// could be frames of animation, but no browser renders them.\n\t\t\tcase 0x21:\n\t\t\t\toffset += 2 // skip introducer and label\n\t\t\t\toffset += getDataBlocksLength(view, offset) // skip this block and following data blocks\n\n\t\t\t\tbreak\n\n\t\t\t// Stop processing on trailer block,\n\t\t\t// all data after this point will is ignored by decoders\n\t\t\tcase 0x3b:\n\t\t\t\toffset = view.length // fast forward to end of buffer\n\t\t\t\tbreak\n\n\t\t\t// Oops! This GIF seems to be invalid\n\t\t\tdefault:\n\t\t\t\t// fast forward to end of buffer\n\t\t\t\toffset = view.length\n\t\t\t\tbreak\n\t\t}\n\t}\n\n\treturn imagesCount > 1\n}\n"],
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