1/* 2 * Copyright (c) 2024 - 2025 Huawei Device Co., Ltd. 3 * Licensed under the Apache License, Version 2.0 (the "License"); 4 * you may not use this file except in compliance with the License. 5 * You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software 10 * distributed under the License is distributed on an "AS IS" BASIS, 11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 * See the License for the specific language governing permissions and 13 * limitations under the License. 14 */ 15 16import type { ImageData } from '../../../model/Interfaces'; 17import { readUInt32BE, toUTF8String } from '../BytesUtils'; 18 19const pngSignature = 'PNG\r\n\x1a\n'; 20const pngImageHeaderChunkName = 'IHDR'; 21const pngFriedChunkName = 'CgBI'; 22 23export const PNG: ImageData = { 24 validate(input) { 25 if (pngSignature === toUTF8String(input, 1, 8)) { 26 let chunkName = toUTF8String(input, 12, 16); 27 if (chunkName === pngFriedChunkName) { 28 chunkName = toUTF8String(input, 28, 32); 29 } 30 if (chunkName !== pngImageHeaderChunkName) { 31 throw new TypeError('Invalid PNG'); 32 } 33 return true; 34 } 35 return false; 36 }, 37 38 calculate(input) { 39 if (toUTF8String(input, 12, 16) === pngFriedChunkName) { 40 return { 41 height: readUInt32BE(input, 36), 42 width: readUInt32BE(input, 32), 43 }; 44 } 45 return { 46 height: readUInt32BE(input, 20), 47 width: readUInt32BE(input, 16), 48 }; 49 }, 50};