Scale Image Using PHP and Maintaining Aspect Ratio

Question

Basically I want to upload an image (which i\'ve sorted) and scale it down to certain constraints such as max width and height but maintain the aspect ratio of the original

Answer 1

I know you are looking for a divisor that will allow resize your image proportionally. Check this demo

How to get our divisor mathematically

lets assume our original image has width x and height y; x=300 and y = 700

Maximum height and maximum width is 200;

First, we will check which dimension of the image is greater than the other. Our height (y) is greater than width(x)

Secondly, we check if our height is greater than our maximum height. For our case, our height is greater than the maximum height. In a case where it less that the maximum height, we set our new height to our original height.

Finally, we look for our divisor as shown below

if y is set to maximum height 200 and max-y=200;
y=max-y, that is 
if y=max-y
what about 
x=?
that is, 
if 700 is resized to 200
what about 300?
700=200
300=?
new width = (200 (new height) * 300(width)) / 700 (height)
so our divisor is
divisor= new height (300) / height(700) 
new width = divisor * width or width / (1/divisor)

and vice versa for the width if it greater than height

if ($width > $height) {
    if($width < $max_width)
        $newwidth = $width;

    else

    $newwidth = $max_width; 


    $divisor = $width / $newwidth;
    $newheight = floor( $height / $divisor);
}
else {

     if($height < $max_height)
         $newheight = $height;
     else
         $newheight =  $max_height;

    $divisor = $height / $newheight;
    $newwidth = floor( $width / $divisor );
}

See the full example and try it using the working demo .