I'm using java pdfBox library to validate single page pdf files with embedded images.
I know that pdf file itself doesen't contain the DPI information.
However the images that have the equal dimensions in the document have different sizes in pixels after extracting and no dpi meta information.
So is it possible to somehow calculate the image sizes relative to pdf page or to extract images with their dpi information (for png or jpeg image files) using pdfBox?
Thanks!
Get the PrintImageLocations.java file from the PDFBox official example source codes. Here's an except of the source, only the last line is by me, and it will output the dpi:
float imageXScale = ctmNew.getXScale();
float imageYScale = ctmNew.getYScale();
System.out.println("position = " + ctmNew.getXPosition() + ", " + ctmNew.getYPosition());
// size in pixel
System.out.println("size = " + imageWidth + "px, " + imageHeight + "px");
// size in page units
System.out.println("size = " + imageXScale + "pu, " + imageYScale + "pu");
// size in inches
imageXScale /= 72;
imageYScale /= 72;
System.out.println("size = " + imageXScale + "in, " + imageYScale + "in");
// size in millimeter
imageXScale *= 25.4;
imageYScale *= 25.4;
System.out.println("size = " + imageXScale + "mm, " + imageYScale + "mm");
System.out.printf("dpi = %.0f dpi (X), %.0f dpi (Y) %n", image.getWidth() * 72 / ctmNew.getXScale(), image.getHeight() * 72 / ctmNew.getYScale());
And here's a sample output:
Found image [X0]
position = 0.0, 0.0
size = 2544px, 3523px <---- pixels
size = 610.56pu, 845.52pu <---- "page units", 1pu = 1/72 inch
size = 8.48in, 11.743334in
size = 215.39198mm, 298.28067mm
dpi = 300 dpi (X), 300 dpi (Y)