Constrain Proportions - Dev Articles

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December 16th, 2002, 06:13 PM

Brian Rosner

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Constrain Proportions

I'm looking for some help on how contraint proportions work. I know when I want to resize a photo in Photoshop all I need to do is supply either the width or hieght and it will automatically determine the apporiate opposite size.

I have read through Ben's article on making thumbnails with PHP and GD, but it seems in that you have to supply both and then the script will determine the size.

Any help would be awesome. Thanks in advance!

Last edited by Brian Rosner : December 16th, 2002 at 06:32 PM.

December 16th, 2002, 07:01 PM

Ben Rowe

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to keep the proportion of the iamge, you need to get the propotion of the resize side to the original side. so you do

pro = orgina_h/resized_h

pro would be say .09 to make it smaller, and 1.1 if you resized it bigger,

then you times the width of the original image by the pro

origina_w * pro

this would give you your resized image, keeping the proportion.

December 16th, 2002, 07:04 PM

jpenn

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PHP Code:


		
			
/* $scale: Percentage to scale the image to */

$scale = '10';



/* Make it work */

$size = GetImageSize( $image );

$width = $size[0];

$height = $size[1];

$scale = $scale/100;

$newwidth = round( $width * $scale );

$newheight = round( $height * $scale );



/*

   Feed the above a 800x600 image and it should

   scale it to 80x60 when using 10% scale.

   Untested - might work - might not...

*/

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