This sample shows how to use mask images to make certain parts of PDF images transparent with the help of Docotic.Pdf library.
You can add a transparent image to a PDF document using one of the PdfDocument.AddImage methods that accept a mask image as a parameter. The mask image must have the same width and height as the image to be made transparent. Pixels of the mask image must use 1 bit per pixel.
To produce the output, PDF viewers will use the image and its mask image. For each position in the output, viewers will do this:
- Get the mask image pixel at the current position.
- If the mask image pixel is black, then get the pixel of the image at the same position and draw it.
- If the mask image pixel is white, draw nothing.
Mask images encode black pixels using 0 bits. For white pixels, the mask images use 1 bits.