降采样

Signed-off-by: tsm <tianshuangming@h-partners.com>

library/index.ets

@@ -66,4 +66,6 @@ export { CropTransformation } from './src/main/ets/transform/CropTransformation'
 
 export { MaskTransformation } from './src/main/ets/transform/MaskTransformation'
 
-export { SepiaTransformation } from './src/main/ets/transform/SepiaTransformation'
+export { SepiaTransformation } from './src/main/ets/transform/SepiaTransformation'
+
+export { DownsampleStrategy } from './src/main/ets/downsampling/DownsampleStartegy'

library/src/main/ets/ImageKnifeDispatcher.ets

@@ -40,6 +40,8 @@ import {
 } from './model/ImageKnifeData'
 import { combineArrayBuffers } from './model/utils';
 import { BusinessError } from '@kit.BasicServicesKit';
+import { Downsampler } from './downsampling/Downsampler';
+import { DownsampleStrategy } from './downsampling/DownsampleStartegy';
 
 export class ImageKnifeDispatcher {
   // 最大并发
@@ -189,7 +191,10 @@ export class ImageKnifeDispatcher {
       fileCacheFolder: ImageKnife.getInstance().getFileCache()?.getCacheFolder(),
       isAnimator:isAnimator,
       moduleName: moduleName == "" ? undefined : moduleName,
-      resName: resName == "" ? undefined : resName
+      resName: resName == "" ? undefined : resName,
+      targetWidth: currentRequest.componentWidth,
+      targetHeight: currentRequest.componentHeight,
+      downsampType: currentRequest.imageKnifeOption.downsampleOf,
     }
 
     if(request.customGetImage == undefined) {
@@ -204,7 +209,7 @@ export class ImageKnifeDispatcher {
         emitter.on(Constants.PROGRESS_EMITTER + memoryKey, (data) => {
           this.progressCallBack(requestList! , data?.data?.value as number)
         });
-        }
+      }
 
       LogUtil.log("ImageKnife_DataTime_getAndShowImage_execute.start:" + currentRequest.imageKnifeOption.loadSrc)
       taskpool.execute(task).then((res: Object) => {
@@ -340,8 +345,8 @@ export class ImageKnifeDispatcher {
           }
         } else {
           if (requestWithSource.source == ImageKnifeRequestSource.SRC && requestWithSource.request.imageKnifeOption.onLoadListener?.onLoadCancel) {
-              // 回调请求成功
-              requestWithSource.request.imageKnifeOption.onLoadListener.onLoadCancel("component has destroyed")
+            // 回调请求成功
+            requestWithSource.request.imageKnifeOption.onLoadListener.onLoadCancel("component has destroyed")
           }
         }
       });
@@ -484,7 +489,7 @@ async function requestJob(request: RequestJobRequest, requestList?: List<ImageKn
             if (data == 200 || data == 206 || data == 204) {
               resBuf = combineArrayBuffers(arrayBuffers)
             } else {
-            loadError = "HttpDownloadClient has error, http code =" + JSON.stringify(data)
+              loadError = "HttpDownloadClient has error, http code =" + JSON.stringify(data)
             }
           }).catch((err: Error) => {
             loadError = err.message;
@@ -505,21 +510,21 @@ async function requestJob(request: RequestJobRequest, requestList?: List<ImageKn
           loadError = "success get image from filecache for key = " + fileKey;
         }
       } else if (request.src.startsWith('datashare://') || request.src.startsWith('file://')) {
-          await fs.open(request.src, fs.OpenMode.READ_ONLY).then(async (file) => {
-            await fs.stat(file.fd).then(async (stat) =>{
-              let buf = new ArrayBuffer(stat.size);
-              await fs.read(file.fd, buf).then((readLen) => {
-                resBuf = buf;
-                fs.close(file.fd);
-              }).catch((err:BusinessError) => {
-                loadError = 'LoadDataShareFileClient fs.read err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
-              })
+        await fs.open(request.src, fs.OpenMode.READ_ONLY).then(async (file) => {
+          await fs.stat(file.fd).then(async (stat) =>{
+            let buf = new ArrayBuffer(stat.size);
+            await fs.read(file.fd, buf).then((readLen) => {
+              resBuf = buf;
+              fs.close(file.fd);
             }).catch((err:BusinessError) => {
-              loadError = 'LoadDataShareFileClient fs.stat err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
+              loadError = 'LoadDataShareFileClient fs.read err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
             })
           }).catch((err:BusinessError) => {
-            loadError ='LoadDataShareFileClient fs.open err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
+            loadError = 'LoadDataShareFileClient fs.stat err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
           })
+        }).catch((err:BusinessError) => {
+          loadError ='LoadDataShareFileClient fs.open err happened uri=' + request.src + " err.msg=" + err?.message + " err.code=" + err?.code;
+        })
       } else { //从本地文件获取
         try {
           let stat = fs.statSync(request.src);
@@ -651,6 +656,20 @@ async function requestJob(request: RequestJobRequest, requestList?: List<ImageKn
       editable: true,
       desiredSize: defaultSize
     };
+    let imageInfo = await imageSource.getImageInfo()
+    if ((request.downsampType !== DownsampleStrategy.NONE && request.downsampType !== undefined) &&
+      request.requestSource == ImageKnifeRequestSource.SRC) {
+      let reqSize =
+        new Downsampler().calculateScaling(typeValue, imageInfo.size.width, imageInfo.size.height, request.targetWidth,
+          request.targetHeight, request.downsampType)
+      opts = {
+        editable: true,
+        desiredSize: {
+          height: vp2px(reqSize.targetHeight),
+          width: vp2px(reqSize.targetWidth)
+        }
+      }
+    }
     await imageSource.createPixelMap(opts)
       .then((pixelmap: PixelMap) => {
         resPixelmap = pixelmap
@@ -663,6 +682,22 @@ async function requestJob(request: RequestJobRequest, requestList?: List<ImageKn
       type:typeValue
     };
   }
+
+  let imageInfo = await imageSource.getImageInfo()
+  if ((request.downsampType !== undefined && request.downsampType !== DownsampleStrategy.NONE) &&
+    request.requestSource == ImageKnifeRequestSource.SRC) {
+    let reqSize =
+      new Downsampler().calculateScaling(typeValue, imageInfo.size.width, imageInfo.size.height, request.targetWidth,
+        request.targetHeight, request.downsampType)
+
+    decodingOptions = {
+      editable: true,
+      desiredSize: {
+        width: reqSize.targetWidth,
+        height: reqSize.targetHeight
+      }
+    }
+  }
   let size = (await imageSource.getImageInfo()).size
   await imageSource.createPixelMap(decodingOptions)
     .then((pixelmap: PixelMap) => {

library/src/main/ets/ImageKnifeOption.ets

@@ -16,6 +16,7 @@ import taskpool from '@ohos.taskpool';
 import common from '@ohos.app.ability.common'
 import { CacheStrategy, ImageKnifeData,EventImage } from './model/ImageKnifeData';
 import { PixelMapTransformation } from './transform/PixelMapTransformation';
+import { DownsampleStrategy } from './downsampling/DownsampleStartegy';
 import { drawing } from '@kit.ArkGraphics2D';
 
 export interface HeaderOptions {
@@ -90,6 +91,8 @@ interface ImageOption {
   onLoadListener?: OnLoadCallBack | undefined;
   onComplete?:(event:EventImage | undefined) => void
   drawingColorFilter?: ColorFilter | drawing.ColorFilter
+  downsampleOf?: DownsampleStrategy
+
 }
 @ObservedV2
 export class ImageKnifeOption {
@@ -121,6 +124,9 @@ export class ImageKnifeOption {
   onLoadListener?: OnLoadCallBack | undefined;
   onComplete?:(event:EventImage | undefined) => void
   drawingColorFilter?: ColorFilter | drawing.ColorFilter
+  // 下采样
+  downsampleOf?: DownsampleStrategy = DownsampleStrategy.NONE
+
   constructor(option?:ImageOption) {
     this.loadSrc = option?.loadSrc == undefined ? "" : option?.loadSrc
     this.placeholderSrc = option?.placeholderSrc
@@ -141,6 +147,7 @@ export class ImageKnifeOption {
     this.onLoadListener = option?.onLoadListener
     this.onComplete = option?.onComplete
     this.drawingColorFilter = option?.drawingColorFilter
+    this.downsampleOf = option?.downsampleOf
   }
 }
 

library/src/main/ets/ImageKnifeRequest.ets

@@ -15,7 +15,7 @@
 import { ImageKnifeOption } from './ImageKnifeOption';
 import common from '@ohos.app.ability.common';
 import { ImageKnifeRequestSource } from './model/ImageKnifeData';
-
+import { DownsampleStrategy } from './downsampling/DownsampleStartegy';
 
 export class ImageKnifeRequest {
   requestState: ImageKnifeRequestState = ImageKnifeRequestState.PROGRESS
@@ -27,18 +27,22 @@ export class ImageKnifeRequest {
   ImageKnifeRequestCallback: ImageKnifeRequestCallback
   componentVersion: number = 0
   headers: Map<string,Object> = new Map<string,Object>()
+  downsampType?: DownsampleStrategy
   constructor(option: ImageKnifeOption,
-              uIAbilityContext: common.UIAbilityContext,
-              width: number,
-              height: number,
-              version: number,
-              ImageKnifeRequestCallback: ImageKnifeRequestCallback) {
+    uIAbilityContext: common.UIAbilityContext,
+    width: number,
+    height: number,
+    version: number,
+    ImageKnifeRequestCallback: ImageKnifeRequestCallback,
+    downsampType?: DownsampleStrategy,
+  ) {
     this.imageKnifeOption = option
     this.context = uIAbilityContext
     this.componentWidth = width
     this.componentHeight = height
     this.componentVersion = version
     this.ImageKnifeRequestCallback = ImageKnifeRequestCallback
+    this.downsampType = downsampType
   }
   // RequestOption调用header对于的方法
   addHeader(key: string, value: Object) {

library/src/main/ets/downsampling/BaseDownsampling.ets

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { DownsampleStrategy } from './DownsampleStartegy';
+
+import { SampleSizeRounding } from './DownsampleUtils';
+
+export interface BaseDownsampling {
+  getName(): string
+
+  getScaleFactor(sourceWidth: number, sourceHeight: number, requestWidth: number, requestHeight: number,downsampType?:DownsampleStrategy): number
+
+  getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestWidth: number,
+    requestHeight: number,downsampType?:DownsampleStrategy): SampleSizeRounding
+}

library/src/main/ets/downsampling/DownsampleStartegy.ets

@@ -0,0 +1,184 @@
+/*
+ * Copyright (C) 2024 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { BaseDownsampling } from './BaseDownsampling';
+import { highestOneBit, SampleSizeRounding } from './DownsampleUtils';
+
+export class FitCenter implements BaseDownsampling {
+  getName() {
+    return "FitCenter"
+  }
+
+  getScaleFactor(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): number {
+    if (downsampType===DownsampleStrategy.FIT_CENTER_QUALITY) {
+      const widthPercentage = requestedWidth / sourceWidth
+      const heightPercentage = requestedHeight / sourceHeight
+      return Math.min(widthPercentage, heightPercentage)
+    } else {
+      const maxIntegerFactor = Math.max(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
+      const a = maxIntegerFactor === 0 ? 1 : 1 / highestOneBit(maxIntegerFactor)
+      return a;
+    }
+  }
+
+  //实现 getSampleSizeRounding 方法
+  getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): number {
+    if (downsampType===DownsampleStrategy.FIT_CENTER_QUALITY) {
+      return SampleSizeRounding.QUALITY;
+    } else {
+      return SampleSizeRounding.MEMORY;
+    }
+
+  }
+}
+
+export class None implements BaseDownsampling {
+  getName(): string {
+    return "DownsampleNone"
+  }
+
+  public getScaleFactor(sourceWidth: number, sourceHeight: number, requestedWidth: number,
+    requestedHeight: number): number {
+    //不进行任何下采样，缩放因子为 1
+    return 1;
+  }
+
+  //实现 getSampleSizeRounding 方法
+  public getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestedWidth: number,
+    requestedHeight: number): SampleSizeRounding {
+    return SampleSizeRounding.QUALITY
+
+  }
+}
+
+
+/*宽高进行等比缩放宽高里面最小的比例先放进去
+然后再更据原图的缩放比去适配另一边*/
+
+export class CenterOutside implements BaseDownsampling {
+  getName() {
+    return "CenterOutside"
+  }
+
+  getScaleFactor(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number): number {
+    const widthPercentage = requestedWidth / sourceWidth;
+    const heightPercentage = requestedHeight / sourceHeight;
+    //返回宽度和高度比例中最大的值
+    return Math.max(widthPercentage, heightPercentage);
+  }
+
+  getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestedWidth: number,
+    requestedHeight: number): SampleSizeRounding {
+    //根据 CenterOutside 的逻辑，总是返回 QUALITY
+    return SampleSizeRounding.QUALITY;
+  }
+}
+
+/*请求尺寸大于实际尺寸不进行放大,按照原图展示*/
+
+export class AtMost implements BaseDownsampling {
+  getName() {
+    return "AtMost"
+  }
+
+  //实现 getScaleFactor 方法
+  getScaleFactor(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number): number {
+    const maxIntegerFactor = Math.ceil(Math.max(sourceHeight / requestedHeight, sourceWidth / requestedWidth));
+    let lesserOrEqualSampleSize = Math.max(1, highestOneBit(maxIntegerFactor));
+    let greaterOrEqualSampleSize = lesserOrEqualSampleSize
+    if (lesserOrEqualSampleSize < maxIntegerFactor) {
+      greaterOrEqualSampleSize = lesserOrEqualSampleSize <<= 1;
+    }
+    greaterOrEqualSampleSize = lesserOrEqualSampleSize << (lesserOrEqualSampleSize < maxIntegerFactor ? 1 : 0)
+    //返回缩放因子
+    return 1 / greaterOrEqualSampleSize
+  }
+
+
+  getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestedWidth: number,
+    requestHeight: number): SampleSizeRounding {
+    //根据 AtMost 的逻辑，总是返回 MEMORY
+    return SampleSizeRounding.MEMORY
+  }
+}
+
+/*宽高进行等比缩放宽高里面最大的比例先放进去
+然后再更据原图的缩放比去适配另一边*/
+export class CenterInside implements BaseDownsampling {
+  getName() {
+    return "CenterInside"
+  }
+
+  getScaleFactor(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): number {
+    //获取 FIT_CENTER 的缩放因子
+    const fitCenterScaleFactor: ESObject =
+      this.getScale(sourceWidth, sourceHeight, requestedWidth, requestedHeight, downsampType);
+    //返回不超过 1 的缩放因子，即尽量缩小图像以适应目标尺寸，但不会放大
+    return Math.min(1, fitCenterScaleFactor);
+
+  }
+
+  getScale(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): number {
+    if (downsampType===DownsampleStrategy.FIT_CENTER_QUALITY) {
+      const widthPercentage = requestedWidth / sourceWidth
+      const heightPercentage = requestedHeight / sourceHeight
+      return Math.min(widthPercentage, heightPercentage)
+    } else {
+      //类似 AT_LEAST,但只要求一个维度或另一个维度大于等于请求的尺寸
+      const maxIntegerFactor = Math.max(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
+      return maxIntegerFactor === 0 ? 1 : 1 / highestOneBit(maxIntegerFactor);
+
+    }
+  }
+
+  getSampleSizeRounding(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): SampleSizeRounding {
+    //如果缩放因子为 1，表示没有缩放，优先选择质量
+    if (this.getScaleFactor(sourceWidth, sourceHeight, requestedWidth, requestedHeight, downsampType) === 1) {
+      return SampleSizeRounding.QUALITY
+    }
+    //否则，使用 FIL_CENTER 的 SampleSizeRounding 值
+    return this.getSampleSize(sourceWidth, sourceHeight, requestedWidth, requestedHeight,downsampType);
+  }
+
+  getSampleSize(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,downsampType:DownsampleStrategy
+    ): SampleSizeRounding {
+    if (downsampType===DownsampleStrategy.CENTER_INSIDE_QUALITY) {
+      return SampleSizeRounding.QUALITY;
+    } else {
+      return SampleSizeRounding.MEMORY;
+    }
+  }
+}
+
+export enum DownsampleStrategy {
+  //请求尺寸大于实际尺寸不进行放大
+  AT_MOST,
+  //两边自适应内存优先
+  FIT_CENTER_MEMORY  ,
+  //两边自适应质量优先
+  FIT_CENTER_QUALITY,
+  //按照宽高比的最大比进行适配内存优先
+  CENTER_INSIDE_MEMORY ,
+  //按照宽高比的最大比进行适配质量优先
+  CENTER_INSIDE_QUALITY,
+  //宽高进行等比缩放宽高里面最小的比例先放进去，然后再根据原图的缩放比去适配
+  CENTER_OUTSIDE,
+  //不进行降采样
+  NONE,
+}

library/src/main/ets/downsampling/DownsampleUtils.ets

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2024 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the 'License');
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an 'AS IS' BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+export enum SampleSizeRounding {
+  /**
+   * Prefer to round the sample size up so that the image is downsampled to smaller than the
+   * requested size to use less memory.
+   */
+  //（内存优先）
+  MEMORY,
+  /**
+   * Prefer to round the sample size down so that the image is downsampled to larger than the
+   * requested size to maintain quality at the expense of extra memory usage.
+   */
+  //（质量优先）
+  QUALITY
+}
+export function highestOneBit(i: number): number {
+  i |= (i >> 1);
+  i |= (i >> 2);
+  i |= (i >> 4);
+  i |= (i >> 8);
+  i |= (i >> 16);
+  return i - (i >>> 1);
+}

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

@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2024 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the 'License');
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an 'AS IS' BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {
+  AtMost,
+  CenterInside,
+  CenterOutside,
+  DownsampleStrategy,
+  FitCenter,
+  None,
+} from './DownsampleStartegy';
+import { highestOneBit, SampleSizeRounding } from './DownsampleUtils';
+
+export interface calculateScaleType {
+  targetWidth: number,
+  targetHeight: number
+}
+
+export class Downsampler {
+  calculateScaling(
+    typeValue: string | null,
+    sourceHeight: number, //原始宽高
+    sourceWidth: number | undefined, //原始宽高
+    requestHeight: number, //请求宽高
+    requestWidth: number, //请求宽高
+    downsampType: DownsampleStrategy | undefined,
+
+  ): calculateScaleType {
+    let degreesToRotate: ESObject = 90;
+    const fileType = typeValue //获取图片类型
+    let powerOfTwoWidth: number | null = null;
+    let powerOfTwoHeight: number | null = null;
+    let targetWidth: number = 0
+    let targetHeight: number = 0
+
+    if (sourceHeight <= 0 || sourceWidth == undefined || sourceWidth == null || sourceWidth <= 0) {
+      throw new Error("Cannot found width or height");
+    }
+    let orientedSourceWidth = sourceWidth;
+    let orientedSourceHeight = sourceHeight;
+    if (this.isRotationRequired(degreesToRotate)) {
+      orientedSourceWidth = sourceHeight;
+      orientedSourceHeight = sourceWidth;
+    }
+    if (requestWidth && !requestHeight) {
+      targetWidth = this.round((requestHeight) * orientedSourceWidth / orientedSourceHeight)
+    } else if (requestHeight && !requestWidth) {
+      targetHeight = this.round((requestWidth) * orientedSourceHeight / orientedSourceWidth)
+    } else if (requestHeight && requestWidth) {
+      targetWidth =
+        requestHeight == sourceWidth ? (this.isRotationRequired(degreesToRotate) ? sourceHeight : sourceWidth) :
+          requestWidth;
+      targetHeight =
+        requestHeight == sourceHeight ? (this.isRotationRequired(degreesToRotate) ? sourceWidth : sourceHeight) :
+          requestWidth;
+    } else {
+      throw new Error("Cannot found width or height");
+    }
+    let exactScaleFactor: number | undefined
+    let rounding: SampleSizeRounding | undefined
+    switch (downsampType) {
+      case DownsampleStrategy.FIT_CENTER_MEMORY || DownsampleStrategy.FIT_CENTER_QUALITY:
+        exactScaleFactor = new FitCenter()
+          .getScaleFactor(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight,downsampType)
+        rounding = new FitCenter()
+          .getSampleSizeRounding(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight,downsampType)
+        break;
+      case DownsampleStrategy.NONE:
+        exactScaleFactor = new None()
+          .getScaleFactor(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        rounding = new None()
+          .getSampleSizeRounding(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        break
+      case DownsampleStrategy.AT_MOST:
+        exactScaleFactor = new AtMost()
+          .getScaleFactor(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        rounding = new AtMost()
+          .getSampleSizeRounding(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        break
+      case DownsampleStrategy.CENTER_INSIDE_MEMORY || DownsampleStrategy.CENTER_INSIDE_QUALITY:
+        exactScaleFactor = new CenterInside()
+          .getScaleFactor(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight,downsampType)
+        rounding = new CenterInside()
+          .getSampleSizeRounding(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight,downsampType)
+        break
+
+      case DownsampleStrategy.CENTER_OUTSIDE:
+        exactScaleFactor = new CenterOutside()
+          .getScaleFactor(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        rounding = new CenterOutside()
+          .getSampleSizeRounding(orientedSourceWidth, orientedSourceHeight, targetWidth, targetHeight)
+        break
+    }
+    if (exactScaleFactor==undefined|| exactScaleFactor <= 0 ) {
+      throw new Error("Cannot round with exactScaleFactor");
+    }
+    if (rounding == undefined) {
+      throw new Error("Cannot round with null rounding");
+    }
+    let outWidth: number = this.round(exactScaleFactor * orientedSourceWidth);
+    let outHeight: number = this.round(exactScaleFactor * orientedSourceHeight);
+    let widthScaleFactor = orientedSourceWidth / outWidth;
+    let heightScaleFactor = orientedSourceHeight / outHeight;
+    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 == 1 && (powerOfTwoSampleSize < (1 / exactScaleFactor))) {
+      powerOfTwoSampleSize = powerOfTwoSampleSize << 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") {
+      powerOfTwoWidth = Math.floor(orientedSourceWidth / powerOfTwoSampleSize);
+      powerOfTwoHeight = Math.floor(orientedSourceHeight / powerOfTwoSampleSize);
+    } else if (fileType === "webp") {
+      powerOfTwoWidth = Math.round(orientedSourceWidth / powerOfTwoSampleSize);
+      powerOfTwoHeight = Math.round(orientedSourceHeight / powerOfTwoSampleSize);
+    } else {
+      powerOfTwoWidth = orientedSourceWidth / powerOfTwoSampleSize;
+      powerOfTwoHeight = orientedSourceHeight / powerOfTwoSampleSize;
+    }
+    let a: calculateScaleType = {
+      "targetWidth": powerOfTwoWidth,
+      "targetHeight": powerOfTwoHeight
+    }
+    return a
+  }
+
+  round(value: number): number {
+    return Math.floor(value + 0.5);
+  }
+
+  isRotationRequired(degreesToRotate: number): boolean {
+    return degreesToRotate == 90 || degreesToRotate == 270;
+  }
+}

library/src/main/ets/key/DefaultEngineKey.ets

@@ -17,6 +17,7 @@ import { ImageKnifeOption } from '../ImageKnifeOption';
 import { IEngineKey } from './IEngineKey';
 import { PixelMapTransformation } from '../transform/PixelMapTransformation';
 import { ImageKnifeRequestSource } from '../model/ImageKnifeData';
+import { DownsampleStrategy } from '../downsampling/DownsampleStartegy';
 
 @Sendable
 export class DefaultEngineKey implements IEngineKey {
@@ -31,6 +32,9 @@ export class DefaultEngineKey implements IEngineKey {
       if (imageKnifeOption.transformation) {
         key += "transformation=" + this.getTransformation(imageKnifeOption.transformation) + ";"
       }
+      if ((imageKnifeOption.downsampleOf !== DownsampleStrategy.NONE && imageKnifeOption.downsampleOf !== undefined)) {
+        key += "downsampleOf" + imageKnifeOption.downsampleOf +"width="+width+"height="+ height
+      }
     }
     return key
   }

library/src/main/ets/model/ImageKnifeData.ets

@@ -18,7 +18,7 @@ import { IEngineKey } from '../key/IEngineKey'
 import { PixelMapTransformation } from '../transform/PixelMapTransformation'
 import common from '@ohos.app.ability.common';
 import { Size } from '@kit.ArkUI'
-
+import { DownsampleStrategy } from '../downsampling/DownsampleStartegy'
 export interface ImageKnifeData {
   source: PixelMap | string,
   imageWidth: number,
@@ -103,6 +103,9 @@ export interface RequestJobRequest {
   fileCacheFolder: string,
   isAnimator?: boolean,
   moduleName?:string,
-  resName?: string
+  resName?: string,
+  targetWidth: number
+  targetHeight: number
+  downsampType?: DownsampleStrategy
 }