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I have many images that I have to put a marking on top center, left center and image center. How can I find where these centers are?

Using a ruler seems lame to me, but I am not an expert and I know you will have a better answer to this. Not to mention, that I often use a special tool that does not have a ruler.

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Whats the special tool that you use? What other tools might be available to you? Photoshop has some alignment options but that's only after you've opened the file, created your layers etc. –  baraboom Jun 27 '11 at 16:52
    
I'd use Perl and ImageMagick to automate this. Some (most?) image editing tools should have an option that displays the x-y coordinates of the cursor position - this makes it fairly easy to mark the middle. –  RedGrittyBrick Jun 27 '11 at 16:54
    
Hi, see my answer. It was soooo simple :). –  JoeM Jun 27 '11 at 16:59
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3 Answers 3

up vote 2 down vote accepted

To answer my question:

Photoshop
Useful for alignment, and simple to do.
Starting with your new image, make a new layer
Fill that layer with any colour with the paintbucket tool
Open your rulers (View > Rulers)
Press Ctrl and T (the shortcut for free transform)
You’ll now see the centre of your image. Drag your rulers to the centre
Now cancel your free transform and delete that layer.

GIMP
Use scale tool (SHIFT+T), select the image, all centers will show up.

So easy, I knew it. :)

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Well sure, easy and a bit tedious but I guess if you do not have very many images the solution is fine. –  baraboom Jun 27 '11 at 17:02
    
Why tedious. Is there a faster way? I did not find any. –  JoeM Jun 27 '11 at 17:05
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Gimp: Guides> new Guides by percent drop one at 50% horizontal and one at 50% vertical to show the center

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Where is such option? I cannot find it. –  JoeM Jun 28 '11 at 13:35
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It's under the Image menu. Image> Guides> New Guides by Percent –  Ele Munjeli Jul 1 '11 at 0:22
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use this formula for finding the center of a rectangle:

( (length of width )/2 ,(length of height )/2 )

find out the size of your image in pixels. for example, if the size is 340 x 168, then the center of this image is: ( 340/ 2 ), (168 / 2) -> 170, 84. just explore photoshop to locate that coordinate

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