How to calculate a proportional size for a given image with not to exceed

Question

I have an area to display an image that has a max size of 240x180

If I have an image of 400x423 how can I calculate a new width and height for that image that best fits into my 240x180 box? (In this case it would be 170x180)

possible duplicate of [Image resizing algorithm](http://stackoverflow.com/questions/3332237/image-resizing-algorithm) — GWW, Jan 27 '11 at 19:28
I've voted to close since the Image resizing algorithm was a duplicate (I was hunt for the wrong keywords). — Jason, Jan 27 '11 at 19:51

score 4 · Accepted Answer · answered Jan 27 '11 at 19:33

there are probably some image libraries that do this well, but the math is pretty simple.

ratio = orig_x * 1.0 / orig_y;

x_oversized = (orig_x > MAX_X);
y_oversized = (orig_y > MAX_Y);

if (x_oversized OR y_oversized)
{
      new_x = min(MAX_X, ratio * MAX_Y);
      new_y = min(MAX_Y, MAX_X / ratio);
}

score 1 · Answer 2 · answered Jan 27 '11 at 19:34

1

Like this?

$newheight = 180; $newwidth = $width * $newheight / $height;

answered Jan 27 '11 at 19:34

Maximilian Ehlers

328
1
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this works assuming the height is the limiting dimension and not the width – jon_darkstar Jan 27 '11 at 20:03
I tried this and it only worked for height, if I am limited by width it does not do the trick. – Jason Jan 27 '11 at 20:16
do a conditional on `height / maxheight > width / maxwidth`. do the above if its true, for the else just swap height and width in the above. – jon_darkstar Jan 28 '11 at 01:11
the one i posted should do the same, whichever u prefer – jon_darkstar Jan 28 '11 at 01:12

How to calculate a proportional size for a given image with not to exceed

2 Answers2