Guides

Background

The background refers to the underlying layer or pattern on the document pages, used to present the fundamental visual effect of the document. Adding a background can alter the document's appearance, making it more personalized or professional. It can be used to emphasize a brand, protect copyright, or enhance the reading experience of the document.

In a PDF document, only one background can exist, and adding a new background to pages containing an existing background will overwrite the old background.

Set Color Background

The steps to set a color background are as follows:

1. Obtain the document's background object.
2. Set the background type to color.
3. Configure the properties of the background.
4. Update the background of the document.

This example shows how to set the color background:

java

// Open document from file path.
CPDFDocument document = new CPDFDocument(context);
document.open(pdfPath, password);
CPDFBackground background = document.getBackground();
background.setType(CPDFBackground.Type.Color);
background.setColor(Color.BLACK);// Background color (image background does not work).
background.setOpacity(1.0F);// Background transparency, the range of 0~1, with the default of 1.
background.setScale(1.0F);// Background tiling scale.
background.setRotation(0);// Background rotation angle, the range of 0~360, the default is 0 (rotate at the centre of the page).
background.setHorizalign(CPDFBackground.CPDFBackgroundAlign.Left);
background.setVertalign(CPDFBackground.CPDFBackgroundAlign.Bottom);
background.setXOffset(0);// The horizontal offset of the background. Positive numbers are shifted to the right, negative numbers are shifted to the left.
background.setYOffset(0);// The vertical offset of the background. Positive numbers are shifted downwards, negative numbers are shifted upwards.
background.setPages("0,1,2");// Set the page range of the background by string, such as "0,3 or 5-7".
background.update();
background.release();

kotlin

// Open document from file path.
val document = CPDFDocument(context)
document.open(pdfPath, password)
val background = document.background
background.apply {
  type = CPDFBackground.Type.Color 
  setImage(bitmap, CPDFImageScaleType.SCALETYPE_fitCenter) // Set images.
  opacity = 1.0F // Background transparency, the range of 0~1, with the default of 1.
  scale = 1.0F // Background tiling scale.
  rotation = 0F // Background rotation angle, the range of 0~360, the default is 0 (rotate at the centre of the page).
  horizalign = CPDFBackground.CPDFBackgroundAlign.Left 
  vertalign = CPDFBackground.CPDFBackgroundAlign.Bottom 
  xOffset = 0F // The horizontal offset of the background. Positive numbers are shifted to the right, negative numbers are shifted to the left.
  yOffset = 0F // The vertical offset of the background. Positive numbers are shifted downwards, negative numbers are shifted upwards.
  pages = "0,1,2" // Set the page range of the background by string, such as "0,3 or 5-7".
  update()
  release()
}

When the document is bound and displayed through CPDFReaderView, after modifying the document pages, you need to call the following method to refresh the view so that the changes take effect immediately:

cpdfReaderView.reloadPages();

Set Image Background

The steps to set an image background are as follows:

1. Obtain the document background object.
2. Set the background type to an image.
3. Specify the background properties.
4. Update the background on the document.

This example shows how to set the image background:

java

// Open document from file path.
CPDFDocument document = new CPDFDocument(context);
document.open(pdfPath, password);
CPDFBackground background = document.getBackground();
background.setType(CPDFBackground.Type.Image);
background.setImage(bitmap, CPDFImageScaleType.SCALETYPE_fitCenter);// Set images.
background.setOpacity(1.0F);// Background transparency, the range of 0~1, with the default of 1.
background.setScale(1.0F);// Background tiling scale.
background.setRotation(0);// Background rotation angle, the range of 0~360, the default is 0 (rotate at the centre of the page).
background.setHorizalign(CPDFBackground.CPDFBackgroundAlign.Left);
background.setVertalign(CPDFBackground.CPDFBackgroundAlign.Bottom);
background.setXOffset(0);// The horizontal offset of the background. Positive numbers are shifted to the right, negative numbers are shifted to the left.
background.setYOffset(0);// The vertical offset of the background. Positive numbers are shifted downwards, negative numbers are shifted upwards.
background.setPages("0,1,2");// Set the page range of the background by string, such as "0,3 or 5-7".
background.update();
background.release();

kotlin

// Open document from file path.
val document = CPDFDocument(context)
document.open(pdfPath, password)
val background = document.background
background.apply {
  type = CPDFBackground.Type.Image 
  setImage(bitmap, CPDFImageScaleType.SCALETYPE_fitCenter) // Set images.
  opacity = 1.0F // Background transparency, the range of 0~1, with the default of 1.
  scale = 1.0F // Background tiling scale.
  rotation = 0F // Background rotation angle, the range of 0~360, the default is 0 (rotate at the centre of the page).
  horizalign = CPDFBackground.CPDFBackgroundAlign.Left // Horizontal alignment of the background.
  vertalign = CPDFBackground.CPDFBackgroundAlign.Bottom // Background vertical alignment.
  xOffset = 0F // The horizontal offset of the background. Positive numbers are shifted to the right, negative numbers are shifted to the left.
  yOffset = 0F // The vertical offset of the background. Positive numbers are shifted downwards, negative numbers are shifted upwards.
  pages = "0,1,2" // Set the page range of the background by string, such as "0,3 or 5-7".
  update()
  release()
}

When the document is bound and displayed through CPDFReaderView, after modifying the document pages, you need to call the following method to refresh the view so that the changes take effect immediately:

cpdfReaderView.reloadPages();

Remove Background

The steps to remove the background are as follows:

1. Obtain the document background object.
2. Delete the document background.

This example shows how to remove background:

java

CPDFBackground background = document.getBackground();
//remove all pages background
background.clear();

kotlin

document.background.clear()

When the document is bound and displayed through CPDFReaderView, after modifying the document pages, you need to call the following method to refresh the view so that the changes take effect immediately:

cpdfReaderView.reloadPages();