PostScript to Images

One of the problems encountered when converting a postscript file to an image format is the loss of image quality. This page describes some things you can try.

Note: You can often avoid converting a postscript file to another format. If you want to annotate a postscript image, use tgif. This program does not require the conversion of a postscript file to an image format.

The program convert is a general conversion program that can handle many different formats including postscript. Try this or xv first. Often, you will lose resolution and the results will be quite poor.

To use xv on the file in-file.ps
• xv in-file.ps (xv will use gs to convert the postscript file to a different format. This may take some time depending on the size of the postscript file).
• Select a rectangular region that you want to save by.
  1. Moving the mouse to one corner of the rectangle.
  2. Press the left mouse button and drag to define the rectangular region.
• Press the right button. (Another window will pop up.)
• Click on Crop.
• Click on Save. Choose a file name and format.

As stated above, when xv or convert converts postscript to some other format, resolution is lost. These programs use ghostscript to convert postscript to the portable pixmap format (ppm) and use 72 dots per inch in the conversion. You can convert a postscript program at a higher resolution as follows.

• gs -sDEVICE=tiff24nc -r300x300 -q -dNOPAUSE -sOutputFile=xxx.tiff -- infile.ps

You may specify a lower or higher resolution. I usually start with 300. If the file size is too big, decrease the resolution. This will also decrease the quality of the image.

You may also want to modify the above command to use "-sDEVICE=tifflzw" instead of "-sDEVICE=tiff24nc". This will use file compression when it stores the files. Most programs that can read tiff images can read files compressed with the lzw compression. There is a significant reduction of the file size using lzw compression - There is no loss of image quality.

You can also convert to a number of different image formats, including ppm, and png. For a list of formats, type gs -help . Look at the list of available devices.

For the best results , I will often convert a postscript file using ghostscript to a tiff image with a resolution of 600 x 600, then use Adobe Photoshop to modify the image.

If these don't work, there are several other things to try. The easiest is to contact Barry Schaudt, schaudt@msi.umn.edu for assistance.

This information is available in alternative formats upon request by individuals with disabilities. Please send email to alt-format@msi.umn.edu or call 612-624-0528.

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