forked from floraachy/ImageKnife
58 lines
2.0 KiB
Plaintext
58 lines
2.0 KiB
Plaintext
/*
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* Copyright (C) 2024 Huawei Device Co., Ltd.
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* Licensed under the Apache License, Version 2.0 (the 'License');
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an 'AS IS' BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { DownsampleStrategy } from './DownsampleStartegy';
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export enum SampleSizeRounding {
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/**
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* Prefer to round the sample size up so that the image is downsampled to smaller than the
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* requested size to use less memory.
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*/
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//（内存优先）
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MEMORY,
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/**
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* Prefer to round the sample size down so that the image is downsampled to larger than the
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* requested size to maintain quality at the expense of extra memory usage.
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*/
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//（质量优先）
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QUALITY
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}
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//找出给定整数 i 中最高位的1（即最左边的1）所代表的值
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export function highestOneBit(i: number): number {
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i |= (i >> 1);
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i |= (i >> 2);
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i |= (i >> 4);
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i |= (i >> 8);
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i |= (i >> 16);
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return i - (i >>> 1);
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}
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export function getScale(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,
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downsampType: DownsampleStrategy
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): number {
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if (downsampType === DownsampleStrategy.FIT_CENTER_MEMORY) {
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const widthPercentage = requestedWidth / sourceWidth
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const heightPercentage = requestedHeight / sourceHeight
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return Math.min(widthPercentage, heightPercentage)
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} else {
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const maxIntegerFactor = Math.max(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
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return maxIntegerFactor === 0 ? 1 : 1 / highestOneBit(maxIntegerFactor);
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}
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}
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//四舍五入
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export function round(value: number): number {
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return Math.floor(value + 0.5);
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} |