HarmonyOS 如何进行图片裁剪

示例参考如下：

//index.ets

import image from '@ohos.multimedia.image';
import { resourceManager } from '@kit.LocalizationKit';
import { RectPosition, ActionType, Position, InitPosition } from '../model/Bean'

const TAG = "IMAGE_CROPPING"

@Entry
@Component
struct Index {
  @Provide pixelMap: image.PixelMap | undefined = undefined;
  @Provide pixelMapBackUp: image.PixelMap | undefined = undefined;
  @Provide imageInfo: image.ImageInfo | undefined = undefined;
  private settings: RenderingContextSettings = new RenderingContextSettings(true);
  private canvasContext: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
  private settings2: RenderingContextSettings = new RenderingContextSettings(true);
  private canvasContext2: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings2);
  private settings3: RenderingContextSettings = new RenderingContextSettings(true);
  private canvasContext3: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings3);
  private actionType: ActionType = ActionType.move;
  private rotateOn: boolean = false
  @State imageArea: RectPosition = {
    x: 0,
    y: 0,
    width: 0,
    height: 0
  };
  private touchPosition: Position = {
    x: 0,
    y: 0,
  };
  private initPosition: InitPosition = {
    x: 0,
    y: 0,
    width: 0,
    height: 0,
  }
  @State isCrop: boolean = false
  @State cropImageInfo: image.ImageInfo | undefined = undefined;
  @State pixelMapChange: boolean = false
  @State @Watch('drawMask') clipRect: RectPosition = {
    x: 0,
    y: 0,
    height: 0,
    width: 0
  };

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      if (this.isCrop) {
        if (this.pixelMapChange) {
          Image(this.pixelMap)
            .width(px2vp(this.cropImageInfo?.size.width))
            .height(px2vp(this.cropImageInfo?.size.height))
            .margin({ top: '10%' })
        } else {
          Image(this.pixelMap)
            .width(px2vp(this.cropImageInfo?.size.width))
            .height(px2vp(this.cropImageInfo?.size.height))
            .margin({ top: '10%' })
        }

      } else {
        Canvas(this.canvasContext)
          .width(px2vp(this.imageInfo?.size.width))
          .height(px2vp(this.imageInfo?.size.height))
          .onReady(() => {
            this.drawImage()
          })
          .onAreaChange((value: Area, newVal: Area) => {
            // 获取图片位置xy
            this.initPosition.x = Math.round(newVal.position.x as number)
            this.initPosition.y = Math.round(newVal.position.y as number)
          })
        // 蒙层
        Canvas(this.canvasContext3)
          .position({
            x: this.initPosition.x,
            y: this.initPosition.y
          })
          .width(px2vp(this.imageInfo?.size.width))
          .height(px2vp(this.imageInfo?.size.height))
        // 裁剪框
        Canvas(this.canvasContext2)
          .position({
            x: this.clipRect.x,
            y: this.clipRect.y
          })
          .width(this.clipRect.width)
          .height(this.clipRect.height)
          .onReady(() => {
            this.drawClipImage()
          })
          .onTouch(event => {
            if (event.type === TouchType.Down) {
              this.isMove(event.target.area, event.touches[0]);
              this.touchPosition = {
                x: event.touches[0].screenX,
                y: event.touches[0].screenY
              }
            } else if (event.type === TouchType.Move) {
              let moveX = event.changedTouches[0].screenX - this.touchPosition.x;
              let moveY = event.changedTouches[0].screenY - this.touchPosition.y;
              this.touchPosition = {
                x: event.changedTouches[0].screenX,
                y: event.changedTouches[0].screenY
              }
              this.moveClipCanvas(moveX, moveY);
            }
          })
      }
      Row() {
        Image($rawfile('rotate.png'))
          .width(40)
          .height(40)
          .onClick(() => {
            this.rotateImage()
          })
      }
      .margin({ top: 50 })
      .height('7%')
      .width('100%')
      .padding(30)

      Row() {
        Image($rawfile('reset.png'))
          .width(40)
          .height(40)
          .onClick(() => {
            this.cancel()
          })
        Image($rawfile('crop.png'))
          .width(40)
          .height(40)
          .onClick(() => {
            this.clipImage()
          })
      }
      .margin({ top: 10 })
      .width('100%')
      .height('7%')
      .padding(30)
      .justifyContent(FlexAlign.SpaceBetween)
    }
    .width('100%')
    .height('100%')
    .backgroundColor('#000000')
  }

  // 旋转图片
  async rotateImage() {
    if (this.rotateOn) {
      await this.pixelMap?.rotate(90)
      const info = await this.pixelMap?.getImageInfo()
      this.cropImageInfo = info
      if (this.pixelMapChange) {
        this.pixelMapChange = false
      } else {
        this.pixelMapChange = true
      }
    }
  }

  // 取消剪切
  cancel() {
    this.pixelMap = this.pixelMapBackUp
    this.isCrop = false
    this.rotateOn = false
  }

  // 判断操作类型
  isMove(area: Area, touch: TouchObject) {
    if (touch.x < 60 && touch.y < 60) { // 左上角
      this.actionType = ActionType.topLeft
    } else if (touch.x < 60 && touch.y > (Number(area.height) - 60)) { // 左下
      this.actionType = ActionType.bottomLeft
    } else if (touch.x > Number(area.width) - 60 && touch.y < 60) { // 右上
      this.actionType = ActionType.topRight
    } else if (touch.x > Number(area.width) - 60 && touch.y > (Number(area.height) - 60)) { // 右下
      this.actionType = ActionType.bottomRight
    } else {
      this.actionType = ActionType.move
    }
  }

  // 绘制背景图
  async drawImage() {
    await this.initData('test.jpg')
    if (this.imageInfo != undefined) {
      this.canvasContext.drawImage(this.pixelMap, 0, 0, px2vp(this.imageInfo.size.width),
        px2vp(this.imageInfo.size.height));
      this.canvasContext.save();
    }
  }

  // 绘制蒙层
  drawMask() {
    this.canvasContext3.clearRect(0, 0, this.imageInfo?.size.width, this.imageInfo?.size.height);
    this.canvasContext3.fillStyle = 'rgba(0,0,0,0.7)';
    this.canvasContext3.fillRect(0, 0, px2vp(this.imageInfo?.size.width), px2vp(this.imageInfo?.size.height));
    this.canvasContext3.clearRect(this.clipRect.x - this.initPosition.x, this.clipRect.y - this.initPosition.y,
      this.clipRect.width, this.clipRect.height);
  }

  // 绘制裁剪框
  drawClipImage() {
    this.canvasContext2.clearRect(0, 0, this.clipRect.width, this.clipRect.height);
    this.canvasContext2.lineWidth = 6
    this.canvasContext2.strokeStyle = '#ffffff'
    this.canvasContext2.beginPath()

    this.canvasContext2.moveTo(0, 20)
    this.canvasContext2.lineTo(0, 0);
    this.canvasContext2.lineTo(20, 0);

    this.canvasContext2.moveTo(this.clipRect.width - 20, 0);
    this.canvasContext2.lineTo(this.clipRect.width, 0);
    this.canvasContext2.lineTo(this.clipRect.width, 20);

    this.canvasContext2.moveTo(0, this.clipRect.height - 20);
    this.canvasContext2.lineTo(0, this.clipRect.height);
    this.canvasContext2.lineTo(20, this.clipRect.height);

    this.canvasContext2.moveTo(this.clipRect.width - 20, this.clipRect.height);
    this.canvasContext2.lineTo(this.clipRect.width, this.clipRect.height);
    this.canvasContext2.lineTo(this.clipRect.width, this.clipRect.height - 20);
    this.canvasContext2.stroke()

    this.canvasContext2.beginPath();
    this.canvasContext2.lineWidth = 0.5;
    let height = Math.round(this.clipRect.height / 3);
    for (let index = 0; index <= 3; index++) {
      let y = index === 3 ? this.clipRect.height : height * index;
      this.canvasContext2.moveTo(0, y);
      this.canvasContext2.lineTo(this.clipRect.width, y);
    }
    let width = Math.round(this.clipRect.width / 3);
    for (let index = 0; index <= 3; index++) {
      let x = index === 3 ? this.clipRect.width : width * index;
      this.canvasContext2.moveTo(x, 0);
      this.canvasContext2.lineTo(x, this.clipRect.height);
    }
    this.canvasContext2.stroke();
  }

  // 获取pixelMap与imageInfo
  async initData(fileName: string) {
    const context: Context = getContext(this);
    const resourceMgr: resourceManager.ResourceManager = context.resourceManager;
    const fileData = await resourceMgr.getRawFileContent(fileName);
    const buffer = fileData.buffer;
    const imageSource: image.ImageSource = image.createImageSource(buffer);
    const pixelMap: image.PixelMap = await imageSource.createPixelMap()
    this.pixelMap = pixelMap
    this.pixelMapBackUp = pixelMap
    const imageInfo = await pixelMap.getImageInfo()
    this.imageInfo = imageInfo
    // 裁剪框初始位置
    this.initPosition.width = px2vp(Math.round(this.imageInfo.size.width))
    this.initPosition.height = px2vp(Math.round(this.imageInfo.size.height))
    this.clipRect.height = px2vp(this.imageInfo.size.height)
    this.clipRect.width = px2vp(this.imageInfo.size.width)
    this.clipRect.x = this.initPosition.x
    this.clipRect.y = this.initPosition.y
  }

  // 裁剪图片
  async clipImage() {
    let x = this.clipRect.x - this.initPosition.x;
    let y = this.clipRect.y - this.initPosition.y;
    console.log('x= ' + x + ' y = ' + y + 'height = ' + this.clipRect.height + 'width = ' + this.clipRect.width)
    await this.pixelMap?.crop({
      x: vp2px(x),
      y: vp2px(y),
      size: { height: vp2px(this.clipRect.height), width: vp2px(this.clipRect.width) }
    })
    this.cropImageInfo = await this.pixelMap?.getImageInfo();
    this.isCrop = true
    this.rotateOn = true
  }

  // 裁剪框位置和大小变化 初始位置为图片的初始坐标 移动的坐标
  moveClipCanvas(moveX: number, moveY: number) {
    let clipRect: RectPosition = {
      x: this.clipRect.x,
      y: this.clipRect.y,
      width: this.clipRect.width,
      height: this.clipRect.height
    }
    switch (this.actionType) {
      case ActionType.move:
        clipRect.x += moveX;
        clipRect.y += moveY;
        break;
      case ActionType.topLeft:
        clipRect.x += moveX;
        clipRect.y += moveY;
        clipRect.width += -moveX;
        clipRect.height += -moveY;
        break;
      case ActionType.topRight:
        clipRect.y += moveY;
        clipRect.width += moveX;
        clipRect.height += -moveY;
        break;
      case ActionType.bottomLeft:
        clipRect.x += moveX;
        clipRect.width += -moveX;
        clipRect.height += moveY;
        break;
      case ActionType.bottomRight:
        clipRect.width += moveX;
        clipRect.height += moveY;
        break;
      default:
        break;
    }

    // 偏移坐标小于初始位置
    if (clipRect.x < this.initPosition.x) {
      clipRect.x = this.initPosition.x;
    }

    if (clipRect.y < this.initPosition.y) {
      clipRect.y = this.initPosition.y;
    }

    // 横坐标限制位置
    if (clipRect.width + clipRect.x > this.initPosition.width + this.initPosition.x) {
      if (this.actionType === ActionType.move) {
        clipRect.x = this.initPosition.width + this.initPosition.x - clipRect.width;
      } else {
        clipRect.width = this.initPosition.width + this.initPosition.x - clipRect.x;
      }
    }

    // 纵坐标限制
    if (clipRect.height + clipRect.y > this.initPosition.height + this.initPosition.y) {
      if (this.actionType === ActionType.move) {

        clipRect.y = this.initPosition.height + this.initPosition.y - clipRect.height;
      } else {

        clipRect.height = this.initPosition.height + this.initPosition.y - clipRect.y;
      }
    }

    this.clipRect = {
      x: Math.round(clipRect.x),
      y: Math.round(clipRect.y),
      width: Math.round(clipRect.width),
      height: Math.round(clipRect.height)
    };
  }
}

model文件夹下的Bean.ets文件：

export interface RectPosition {
  x: number;
  y: number;
  height: number;
  width: number;
}

export enum ActionType {
  topLeft,
  topRight,
  bottomLeft,
  bottomRight,
  move
}

export interface Position {
  x: number;
  y: number;
}


export interface InitPosition {
  x: number;
  y: number;
  width: number;
  height: number;
}