0

Is there a php function which will do image resizing math itself but not create a new file?

I created a simple proportionally-resize-an-image math script and I realized there is more to it than just geometry, such as aspect ratio and such. Basic geometry math squashes the image a little.

If anyone is curious, it's simply to give the user a preview of image dimensions should they choose to download, but I'd rather not clutter up the server with tons of size variations of similar images :D.

Thanks.

edit: Per request, here is the key part of the resizing code: 

$ratio = min( $resize_to / $width, $resize_to/ $height );   

$width  = $ratio * $width; 

$height = $ratio * $height;

When I see the values output, I simply do a resize in photoshop using the values and the photoshop version squashes (I do this as a visual test), so I assume my code is faulty.

cb4
  • 6,689
  • 7
  • 45
  • 57
Orangeman555
  • 1,179
  • 2
  • 21
  • 45

2 Answers2

3

The math required to scale an image while respecting aspect ratio is pretty straightforward. Some pseudo code:

original_width = <width of image before resizing>
original_height = <height of image before resizing>

new_width = <the max width desired for the resized image>
new_height = <the max height desired for the resized image>

if original_width >= original_height
  ratio = original_width / original_height
  new_height = new_width / ratio
else 
  ratio = original_height / original_width
  new_width = original_height / ratio
end

print "Width: " + new_width
print "Height: " + new_height

The above can probably be significantly improved but I just meant to illustrate the point.

regulatethis
  • 2,322
  • 14
  • 17
  • Strangely this is pretty much what I was doing. Let me plug this in and see if I get a different result. Thanks for the help! – Orangeman555 Jan 01 '13 at 23:29
0

This is funny. I was resizing one file, then checking another in photoshop. Human error. Went around the block to cross the street and had already crossed the street without knowing it..

Orangeman555
  • 1,179
  • 2
  • 21
  • 45