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转换指定页面或指定区域为图片

场景介绍​

PDF文档页面转换为图片，或将页面的指定区域转换为图片时使用。

接口说明​

接口名描述
getPagePixelMap(): image.PixelMap获取当前页的图片。
getCustomPagePixelMap(matrix: PdfMatrix, isGray: boolean, drawAnnotations: boolean): image.PixelMap获取指定PdfPage区域的图片内容。
getAreaPixelMap(matrix: PdfMatrix, bitmapwidth: number, bitmapHeight: number, isGray: boolean, drawAnnotations: boolean): image.PixelMap获取指定PdfPage区域的图片内容，并指定图片的宽和高。
getAreaPixelMapWithOptions(matrix: PdfMatrix, bitmapwidth: number, bitmapHeight: number, options?: PixelOptions): image.PixelMap获取指定PdfPage区域的图片内容，并指定图片的宽和高等参数。

示例代码​

  1. 调用loadDocument方法加载PDF文档。

  2. 调用getPage方法获取某个页面。

  3. 调用getPagePixelMap，getAreaPixelMapWithOptions或getCustomPagePixelMap方法获取当前页面或者页面区域，这时获取的是image.PixelMap图像类型。

  4. 将image.PixelMap图像类型转化为二进制图片文件并保存，参考以下方法pixelMap2Buffer。

    import { pdfService } from '@kit.PDFKit';
    import { image } from '@kit.ImageKit';
    import { fileIo as fs } from '@kit.CoreFileKit';
    import { BusinessError } from '@kit.BasicServicesKit';
    import { hilog } from '@kit.PerformanceAnalysisKit';

    @Entry
    @Component
    struct PdfPage {
      private pdfDocument: pdfService.PdfDocument = new pdfService.PdfDocument();
      private context = this.getUIContext().getHostContext() as Context;
      private loadResult: pdfService.ParseResult = pdfService.ParseResult.PARSE_ERROR_FORMAT;

      aboutToAppear(): void {
        // 确保沙箱目录有input.pdf文档
        let filePath = this.context.filesDir + '/input.pdf';
        this.loadResult = this.pdfDocument.loadDocument(filePath);
      }

      // 将 pixelMap 转成图片格式
      pixelMap2Buffer(pixelMap: image.PixelMap): Promise<ArrayBuffer> {
        return new Promise((resolve, reject) => {
          /**
           设置打包参数
           format：图片打包格式
           quality：JPEG 编码输出图片质量
           bufferSize：图片大小
           */
          let packOpts: image.PackingOption = { format: 'image/jpeg', quality: 98 }
          // 创建ImagePacker实例
          const imagePackerApi = image.createImagePacker()
          imagePackerApi.packToData(pixelMap, packOpts).then((buffer: ArrayBuffer) => {
            resolve(buffer)
          }).catch((err: BusinessError) => {
            reject()
          })
        })
      }

      build() {
        Column() {
          // 获取为图片并保存到应用沙箱
          Button('getPagePixelMap').onClick(async () => {
            if (this.loadResult === pdfService.ParseResult.PARSE_SUCCESS) {
              let page = this.pdfDocument.getPage(0)
              let pixmap: image.PixelMap = page.getPagePixelMap();
              if (!pixmap) {
                return
              }
              const imgBuffer = await this.pixelMap2Buffer(pixmap)
              try {
                const file =
                  fs.openSync(this.context.filesDir + `/${Date.now()}.png`, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
                await fs.write(file.fd, imgBuffer)
                // 关闭文档
                await fs.close(file.fd)
              } catch (e) {
                let error: BusinessError = e as BusinessError;
                hilog.error(0x0000, 'PdfPage', `Code: ${error.code}, message: ${error.message} `);
              }
            }
          })
          // 获取指定PdfPage区域的图片内容。
          Button('getCustomPagePixelMap').onClick(async () => {
            if (this.loadResult === pdfService.ParseResult.PARSE_SUCCESS) {
              let page = this.pdfDocument.getPage(0);
              let matrix = new pdfService.PdfMatrix();
              matrix.x = 100;
              matrix.y = 100;
              matrix.width = 500;
              matrix.height = 500;
              matrix.rotate = 0;
              let pixmap: image.PixelMap = page.getCustomPagePixelMap(matrix, false, false);
              if (!pixmap) {
                return;
              }
              const imgBuffer = await this.pixelMap2Buffer(pixmap);
              try {
                const file =
                  fs.openSync(this.context.filesDir + `/${Date.now()}.jpeg`, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
                await fs.write(file.fd, imgBuffer);
                // 关闭文件
                await fs.close(file.fd);
              } catch (e) {
                let error: BusinessError = e as BusinessError;
                hilog.error(0x0000, 'PdfPage', `Code: ${error.code}, message: ${error.message} `);
              }
            }
          })
          // 获取指定PdfPage区域的图片内容
          Button('getAreaPixelMap').onClick(async () => {
            if (this.loadResult === pdfService.ParseResult.PARSE_SUCCESS) {
              //获取对应的page
              let page = this.pdfDocument.getPage(0);
              let matrix = new pdfService.PdfMatrix();
              //设置matrix来控制需要获取的区域
              matrix.x = 100;
              matrix.y = 100;
              matrix.width = 500;
              matrix.height = 500;
              matrix.rotate = 0;
              let pixmap: image.PixelMap = page.getAreaPixelMap(matrix, 400, 400, true, false);
              if (!pixmap) {
                return
              }
              const imgBuffer = await this.pixelMap2Buffer(pixmap)
              try {
                const file =
                  fs.openSync(this.context.filesDir + `/${Date.now()}.bmp`, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
                await fs.write(file.fd, imgBuffer)
                // 关闭文件
                await fs.close(file.fd);
              } catch (e) {
                let error: BusinessError = e as BusinessError;
                hilog.error(0x0000, 'PdfPage', `Code: ${error.code}, message: ${error.message} `);
              }
            }
          })
          // 获取指定PdfPage区域的图片内容
          Button('getAreaPixelMapWithOptions').onClick(async () => {
            if (this.loadResult === pdfService.ParseResult.PARSE_SUCCESS) {
              //获取对应page
              let page = this.pdfDocument.getPage(0);
              let matrix = new pdfService.PdfMatrix();
              //设置matrix来控制需要获取的区域
              matrix.x = 100;
              matrix.y = 100;
              matrix.width = 500;
              matrix.height = 500;
              matrix.rotate = 0;
              //设置pixelmap是否黑白，背景是否透明等参数
              let options = new pdfService.PixelOptions();
              options.isGray = false;
              options.drawAnnotations = true;
              options.isTransparent = true;
              let pixmap: image.PixelMap = page.getAreaPixelMapWithOptions(matrix, 400, 400, options);
              if (!pixmap) {
                return
              }
              const imgBuffer = await this.pixelMap2Buffer(pixmap)
              try {
                const file =
                  fs.openSync(this.context.filesDir + `/${Date.now()}.bmp`, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
                await fs.write(file.fd, imgBuffer)
                // 关闭文件
                await fs.close(file.fd);
              } catch (e) {
                let error: BusinessError = e as BusinessError;
                hilog.error(0x0000, 'PdfPage', `Code: ${error.code}, message: ${error.message} `);
              }
            }
          })
        }
      }
    }