将图像的像素高度转换为图形对象使用的打印尺寸

As part of a print procedure of my application I'm trying to print a list of images scaled down to a specified width and placed one below the other. The problem is I can not figure out how to transform the height in pixels of the images to the height in the units used by the graphics object during printing. How do I calculate the imageHeightPrint variable correctly?As part of a print procedure of my application