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Using GIMP to Create a PNG file

justinkuojustinkuoCertifier
I have been using GIMP for converting certificates and maps into PNG files for posting on the USATF Certified Course database. The files for the database must be PNG files of 2550 x 3300 pixels and must have a size of less than 400 kB. GIMP is the free image editing program that is roughly equivalent to Adobe Photoshop or Jasc Paintshop Pro. GIMP is available at www.gimp.org.

I put together a short slide show with instructions on how to use GIMP to create a PNG file.



There are plenty of other methods to accomplish the same. For example, Adobe Acrobat Pro allows one to export a PDF file to PNG, JPG, TIFF, etc. ImageMagick, the command line utility, will convert almost any image file into another format.

Thank you. -- Justin
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AdminAdminMember
Very nice Justin. Thanks!

The Mac version of Gimp does not have Export, so you do a Save As instead. After that though, it is pretty much as you describe.

One other nice feature of that Mode dialogue is the 1-bit option. I sometimes get B&W maps that have been scanned in greyscale so they end up with "dirty" backgrounds that make the PNG files much larger than they need to be. Saving the image in 1-bit B&W cleans that up, makes better looking B&W maps, and results in smaller PNGs.
genenewmangenenewmanRRTC Chairman
You guys may know this, but here is what I discovered for converting large png files to smaller ones.

Using Gimp-2 for PNG that are large and wrong dimensions
1. Open program and drag png to screen, go to Image/Mode/Indexed -> select max colors “9” (Note if you make it smaller the like “2” it will create a smaller file)
2. Click Convert, this will be a Gimp file
3. Go to Image/Canvas Size and adjust size to 2550 x 3300 and select resize
4. Go to Image/Scale Image and set “x” & “y” resolution to 300dpi, then click scale(Interpolation is cubic -I don’t know what the others do?)
5.Go to File and choose Export and now select PNG on bottom rignt(rename file on upper left) and export this file
justinkuojustinkuoCertifier
When using GIMP to adjust the image canvas size, you may need to break the Chain that appears just to the right of the Width and Height. If the chain is not broken, both the Width and the Height will keep the same relative ratio to each other.



For example, if the current image is 2560 x 3300 pixels, and you try to change the width of the canvas to 2550, the height will automatically change to 3287. Break the Chain and you can change it to any ratio you desire. You can break the Chain by clicking on it. -- Justin
justinkuojustinkuoCertifier
Do leave a white border on all 4 sides of the image. The border is necessary because some printers are unable to print closer than 1/4" from the edge of the paper and because the paper may feed off-center. I would recommend a minimum of 1/4" (75 pixels) from the four edges.

To keep the math simple, I leave 100 pixels (1/3") on each of the 4 sides. My maximum visible image size is 2350 x 3100 pixels. -- Justin
Last edited by justinkuo

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