Calculate nearest possible dimension value PHP (keeping ratio) - php

Question

I am trying to implement API for image resizing. It is created not exactly for image processing, this is only one part/feature of API.
What I want to implement.
I have url for retrieving image from server it looks like
mywebpage.com/api/product/42/image
This url will return URL to full image of product with id 42.
Everything is ok.
We can specify desired size with GET parameters like this
mywebpage.com/api/product/42/image?width=200&height=300
It also looks fine
But my question if following.
As we can have different images on server with different dimension and aspect ratio, I need to keep this ratio while resizing.
For example I need image to fit 200x300 container but I have 1024x576 (16:9) image on the server. I need to resize this image but keep initial aspect ratio(16:9) but to fit desired container.
How can I efficiently calculate new image size to return depending on incoming desired dimension and current image aspect ratio.
I want to thank everyone in advance for any help or advises.

Answer 1

Here is a script I used to make similar thing. Quite old , so may be not up to date.
<?php
if( isset($_GET["width"]) && is_numeric($_GET["width"]))
$target_width = intval($_GET["width"]);
else
$target_width= 200;//default value
if( isset($_GET["height"]) && is_numeric($_GET["height"]))
$target_height = intval($_GET["width"]);
else
$target_height= 300;//default value
if( isset($_GET["id"]) && is_numeric($_GET["id"]))//prevent any unwanted filesystem access
$original_image_path = "img/products/$id.jpg";
else
$original_image_path = "placeholder.png"
//http://php.net/manual/fr/function.getimagesize.php
$image_size = getimagesize($original_image_path);
//get the ratio of the original image
$image_ratio= $image_size[1]/ $image_size[0];
$original_image = imagecreatefromjpeg($original_image_path);
$new_image = imagecreatetruecolor($target_width, $image_ratio * $target_width);
//paints the image in white
//http://php.net/manual/en/function.imagefill.php
//http://php.net/manual/en/function.imagecolorallocatealpha.php
imagefill( $new_image, 0, 0, imagecolorallocatealpha($new_image, 255,255,255,127) );
imagesavealpha($new_image, TRUE);
/*
Copies the original to the new, preserving the ratio.
The original image fills all the width of the new,
and is placed on the top of the new.
http://php.net/manual/en/function.imagecopyresized.php
*/
imagecopyresized(
$new_image,$original_image,
0,0,
0,0,
$target_width,$image_ratio * $target_width,
$image_size[0],$image_size[1]
);
//image is returned in response to the request
header ("Content-type: image/png");
imagepng( $new_image );
?>

Answer 2

Well if you need to always fit a container of 200x300 (or what ever is passed through the URL), you may not because able to simply resize it because as you are aware it will affect the images aspect ratio.
If this is the case what you can do is resize the image to the closest size then crop the remainder of the image.
I assume you will be using imagemagick for this. Have you checked out the documentation? The cropThumbnailImage method does what I just explained.
Example usage:
/* Read the image */
$im = new imagick( "test.png" );
/* create the thumbnail */
$im->cropThumbnailImage( 80, 80 );
/* Write to a file */
$im->writeImage( "th_80x80_test.png" );
http://php.net/manual/en/imagick.cropthumbnailimage.php