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update library/src/main/ets/downsampling/Downsampler.ets. 

简化代码

Signed-off-by: 田双明 <tianshuangming@h-partners.com>
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田双明 2024-09-26 01:53:22 +00:00 committed by Gitee
parent b2af4e1958
commit fe9235d8b1
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1 changed files with 33 additions and 35 deletions
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68
library/src/main/ets/downsampling/Downsampler.ets
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@ -29,53 +29,50 @@ export interface calculateScaleType {
export class Downsampler {
calculateScaling(
typeValue: string | null,
sourceWidth: number | undefined, //原始宽高
typeValue: string,
sourceWidth: number, //原始宽高
sourceHeight: number, //原始宽高
requestWidth: number, //请求宽高
requestHeight: number, //请求宽高
downsampType: DownsampleStrategy | undefined,
downsampType: DownsampleStrategy,
): calculateScaleType {
const fileType = typeValue //获取图片类型
let targetWidth: number | null = null;//降采样之后的宽
let targetHeight: number | null = null;//降采样之后的高
if (sourceHeight <= 0 || sourceWidth == undefined || sourceWidth == null || sourceWidth <= 0) {
throw new Error("Cannot found width or height")
}
if(downsampType===undefined){
throw new Error("Cannot found downsampType");
if (sourceHeight <= 0 || sourceWidth <= 0) {
throw new Error("非法宽高 sourceHeight sourceWidth")
}
let downsampler = this.getDownsampler(downsampType);
let exactScaleFactor : number = downsampler.getScaleFactor(sourceWidth, sourceHeight, requestWidth, requestHeight, downsampType);
let rounding: SampleSizeRounding= downsampler.getSampleSizeRounding(sourceWidth, sourceHeight, requestWidth, requestHeight, downsampType);//采样类型
if (exactScaleFactor==undefined|| exactScaleFactor <= 0 ) {
throw new Error("Cannot round with exactScaleFactor");
let exactScaleFactor: number =
downsampler.getScaleFactor(sourceWidth, sourceHeight, requestWidth, requestHeight, downsampType);
let rounding: SampleSizeRounding =
downsampler.getSampleSizeRounding(sourceWidth, sourceHeight, requestWidth, requestHeight, downsampType); //采样类型
//原始宽高和缩放系数的乘积
let outSize = {
width: this.round(exactScaleFactor * sourceWidth),
height: this.round(exactScaleFactor * sourceHeight)
}
let outWidth: number = this.round(exactScaleFactor * sourceWidth);//原始宽和缩放系数的乘积
let outHeight: number = this.round(exactScaleFactor * sourceHeight);//原始高和缩放系数的乘积
let widthScaleFactor = sourceWidth / outWidth;//计算的缩放因子
let heightScaleFactor = sourceHeight / outHeight;//计算的缩放因子
let scaleFactor = rounding ==SampleSizeRounding.QUALITY ? Math.max(widthScaleFactor, heightScaleFactor) :
Math.min(widthScaleFactor, heightScaleFactor) //将整型的缩放因子转换为2的次幂采样大小
let powerOfTwoSampleSize: number = scaleFactor;
powerOfTwoSampleSize = Math.max(1, highestOneBit(scaleFactor))
if (rounding == 0 && (powerOfTwoSampleSize < (1 / exactScaleFactor))) {
powerOfTwoSampleSize = powerOfTwoSampleSize << 1;
let scaleFactor =
rounding == SampleSizeRounding.QUALITY ? Math.max(sourceWidth / outSize.width, sourceHeight / outSize.height) :
Math.min(sourceWidth / outSize.width, sourceHeight / outSize.height) //将整型的缩放因子转换为2的次幂采样大小
scaleFactor = Math.max(1, highestOneBit(scaleFactor))
if (rounding == 0 && (scaleFactor < (1 / exactScaleFactor))) {
scaleFactor = scaleFactor << 1;
}
//基于上一步得出的采样大小，根据不同的图片类型，计算采样后的图片尺寸
if (fileType === "png") {
targetWidth = Math.floor(sourceWidth / powerOfTwoSampleSize);
targetHeight = Math.floor(sourceHeight / powerOfTwoSampleSize);
} else if (fileType === "webp") {
targetWidth = Math.round(sourceWidth / powerOfTwoSampleSize);
targetHeight = Math.round(sourceHeight / powerOfTwoSampleSize);
if (typeValue === "png") {
return {
targetWidth: Math.floor(sourceWidth / scaleFactor),
targetHeight: Math.floor(sourceHeight / scaleFactor)
}
} else if (typeValue === "webp") {
targetWidth = Math.round(sourceWidth / scaleFactor);
targetHeight = Math.round(sourceHeight / scaleFactor);
} else {
targetWidth = sourceWidth / powerOfTwoSampleSize;
targetHeight = sourceHeight / powerOfTwoSampleSize;
targetWidth = sourceWidth / scaleFactor;
targetHeight = sourceHeight / scaleFactor;
}
return { targetWidth, targetHeight }
}
getDownsampler(downsampType:DownsampleStrategy) {
getDownsampler(downsampType: DownsampleStrategy) {
switch (downsampType) {
case DownsampleStrategy.FIT_CENTER_MEMORY:
case DownsampleStrategy.FIT_CENTER_QUALITY:
@ -93,6 +90,7 @@ export class Downsampler {
throw new Error('Unsupported downsampling strategy');
}
}
round(value: number): number {
return Math.floor(value + 0.5);
}