目录

Adding and Deleting Backgrounds

You can add a background image or background color to a specified page and set attributes such as size, rotation, opacity, and position. The following image formats are supported: .png, .bmp, and .jpeg.

API Description

API Name Description
addBackground(info: BackgroundInfo, startIndex: number, endIndex: number, oddPages: boolean, evenPages: boolean): void Adds a background to a PDF document.
removeBackground(): boolean Removes the background of a PDF document.

The addBackground method is time-consuming as it involves iterating through each page to add backgrounds. For documents with many pages, it is recommended that you process them in a thread.

Sample Code

Adding a background:

  1. Call the loadDocument method to load a PDF document.

  2. Instantiate the BackgroundInfo class and set related attributes, including size, rotation, opacity, and position.

  3. Call the addBackground method to add a background.

  4. Save the PDF document to the app sandbox.

Deleting a background:

  1. Call the loadDocument method to load a PDF document.

  2. Call the removeBackground method to remove the background.

  3. Save the PDF document to the app sandbox.

import { pdfService } from '@kit.PDFKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
 // ...
@Entry
@Component
struct BackgroundPage {
  private pdfDocument: pdfService.PdfDocument = new pdfService.PdfDocument();
  private context = this.getUIContext().getHostContext() as Context;

  build() {
    Column() {
     // ...
        Button('addBackground').onClick(async () => {
            // Ensure that the input.pdf document exists in the src/main/resources/resfile project directory.
          let filePath = this.context.resourceDir + '/input.pdf';
          let res = this.pdfDocument.loadDocument(filePath);
          if (res === pdfService.ParseResult.PARSE_SUCCESS) {
            let bginfo: pdfService.BackgroundInfo = new pdfService.BackgroundInfo();
            // Ensure that the img.jpg file exists in the src/main/resources/resfile project directory.
            bginfo.imagePath = this.context.resourceDir + '/img.jpg';
            bginfo.backgroundColor = 50;
            bginfo.isOnTop = true;
            bginfo.rotation = 45;
            bginfo.scale = 0.5;
            bginfo.opacity = 0.3;
            bginfo.verticalAlignment = pdfService.BackgroundAlignment.BACKGROUND_ALIGNMENT_TOP;
            bginfo.horizontalAlignment = pdfService.BackgroundAlignment.BACKGROUND_ALIGNMENT_LEFT;
            bginfo.horizontalSpace = 1.0;
            bginfo.verticalSpace = 1.0;
            this.pdfDocument.addBackground(bginfo, 0, 2, true, true);
            let outPdfPath = this.context.filesDir + '/testAddBackground.pdf';
            let result = this.pdfDocument.saveDocument(outPdfPath);
            hilog.info(0x0000, 'BackgroundPage', 'addBackground %{public}s!', result ? 'success' : 'fail');
          }
          this.pdfDocument.releaseDocument();
        })
        Button('removeBackground').onClick(async () => {
          let filePath = this.context.filesDir + '/testAddBackground.pdf';
          let res = this.pdfDocument.loadDocument(filePath);
          if (res === pdfService.ParseResult.PARSE_SUCCESS && this.pdfDocument.hasBackground()) {
            let removeResult = this.pdfDocument.removeBackground();
            if (removeResult) {
              let outPdfPath = this.context.filesDir + '/removeBackground.pdf';
              let result = this.pdfDocument.saveDocument(outPdfPath);
              hilog.info(0x0000, 'BackgroundPage', 'removeBackground %{public}s!', result ? 'success' : 'fail');
            }
          }
          this.pdfDocument.releaseDocument();
        })
           // ...
    }
  }
}