October 16, 2001 - Pixels to Inches Conversion | WebReference

October 16, 2001 - Pixels to Inches Conversion

Yehuda Shiran October 16, 2001
Pixels to Inches Conversion
Tips: October 2001

Yehuda Shiran, Ph.D.
Doc JavaScript

When you are dealing with page layout and document formatting, you need to be able to convert pixels to inches and vice versa. Suppose you get the margin specification in inches, and you need to format the page using the style object's pixel-based properties. One way to go about it is to set the location of an invisible marker in inches and then query its value in a script, yielding the same value in pixels. Let's see an example.

The following IMG tag defines an invisible marker, one inch away from the left edge of the window, and one inch below the top edge of the window:

<IMG ID="ratiomarker" CLASS="mmarker" STYLE="visibility:hidden;
 left:1in; top:1in; position: absolute" SRC="marker.gif" 
 WIDTH="15" HEIGHT="15" BORDER="0">
Click here to print the offset of ratiomarker. Since the invisible marker's offset is one inch in the IMG tag, the returned value offsetLeft is the conversion factor, pixels per inch. Also, notice that the marker style must be defined with absolute positioning.