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

/*
 * 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,
}