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I am a totally blind computer user.

I encountered an accessibility barrier when I was attempting to use the site http://www.vitalchek.com/ to order a birth certificate. They require you to scan or take a picture of your state ID or vehicle operator's license.

The image I uploaded was rejected because it was under 300 DPI. I have no one who is tech-savvy to help me resize it, so I'm wondering if there are any tools that are accessible.

I used my iPhone's camera to take a picture of my state ID.

  • Can you not use the same program you used to re-scan and set the DPI to the target amount? Depending on your file, Scaling up the file you already have may or may not result in an image that is worse in terms of clarity. if you can give us the info on the file we would know more about the possibilities. If it is possible someone may be able to do it for you by you emailing the file to them or posting it someplace it can modified. – Alaska Man Mar 7 '18 at 23:26
  • I'll edit the question, but I used my iPhone to take the picture. the iPhone uses VoiceOver. I can probably contact Apple to see if they have any recommendations. I don't want to share this photo with anyone because it has sensative personal information. – HeavenlyHarmony Mar 7 '18 at 23:51
  • Of coarse. Perhaps you have a friend with camera or scanner? if you are using an apple computer i can tell you how to use preview, ( it is built into the operating system, ) to change the dpi of your image. – Alaska Man Mar 8 '18 at 0:21
  • I don't have a working Mac right now. I have Windows 10. I just called Apple, but their only recommendation is that I use a photo-converting web site like Zamzar or Comvert files dot com – HeavenlyHarmony Mar 8 '18 at 0:39
  • 3
    Images have no real DPI, so by default the files almost all say 72 DPI. What you need is a tool to change that part of the EXIF info. I suspect it can be done by command line tools like ExifTool but I've never done it, so this is not an answer. – Itai Mar 8 '18 at 4:36
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The image I uploaded was rejected because it was under 300 DPI.

The DPI is just a number which has no relevance to a digital image. It relates only to printing and not the quality or resolution of the image itself.

If you change the number to 300 DPI in an editor, it should be accepted.

As you have Windows 10 and presumably use assistive technology to e.g. read screen dialogs, I suggest trying the following.

  • Install GIMP which is a free image editing application. GIMP is available at this webpage. I use GIMP myself.

  • Open your image in GIMP.

  • Now go to the menu option Image > Print Size. This will open a dialog box that let you set the DPI. There are two fields in the dialog labeled "X resolution" and "Y resolution" - you can ignore the other fields. Change the "X resolution" to 300 and the "Y resolution" will change automatically when you press TAB. Once done, press the OK button.

  • Now go to the menu option File > Export As and you can save the file under a new name. That saved file will have the DPI fields set at 300 DPI.

This works on my Linux setup, and should work the same on Windows 10.

I have tried to make the instructions as clear as possible given that you are blind, but get back to me (using comments) if there is a problem and I'll try and help.

Command Line

As the OP asked for a command line option in Linux I can tell you the simplest way is to use ImageMagick.

You need to do this :

  • convert input.jpg -units PixelsPerInch -density 300 output.jpg

With the filenames changed of course.

Note the "-units PixelsPerInch" option. This is absolutely essential or the file will be marked with an unidentified unit type and not render properly in print applications.

Note that I checked this very carefully using my own Linux setup and checked output rendered by Latex and the PixelsPerInch part is essential to get valid rendering. People sometimes leave this out and it seems to be a source of problems when they actually print the image.

  • Say, I use Linux myself. I am primarily into command-line, since that's how I manage my server, so I wonder if there is something similar. I'll have to try it. Could I use GIMP to edit photos if Stack Exchange rejects them because it's too big? – HeavenlyHarmony Mar 9 '18 at 0:19
  • I have edited the answer to add command line instructions using ImageMagick. – StephenG Mar 9 '18 at 0:57
  • For additional info on DPI and resolution in general, check out the Photo Taco podcast on the subject. Just search for "Photo Taco DPI". Should be the page titled "DPI with Don Komarechka [Photo Taco]".Or use this link – Hughman Mar 9 '18 at 4:43

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