scale an image proportionally without knowing both dimensions

Question

$newimg = imagecreatefromjpeg($tempname);

Now I need to scale this image proportionally but don't know both dimensions in advance.

$newimg = imagescale($newimg, 160, auto, IMG_BICUBIC);  //doesn't work

or

$newimg = imagescale($newimg, auto, 160, IMG_BICUBIC);  // doesn't work

Is there a way to say auto or something to calculate width or height automatically.

If no, how can I calculate this?

The accepted solution here doesn't work. I doesn't keep aspect ratio.

Possible duplicate of [Scale Image Using PHP and Maintaining Aspect Ratio](https://stackoverflow.com/questions/16774521/scale-image-using-php-and-maintaining-aspect-ratio) — Himanshu Upadhyay, Apr 30 '18 at 06:40
@HimanshuUpadhyay, accepted solution on your link doesn't work. It doesn't keep aspect ratio. You can see in comments. — qadenza, Apr 30 '18 at 06:43
Not sure where you got `auto`—there's no such constant in PHP and you should be getting a notice. Have you tried the documented default value, `-1`? Also, what's your PHP version? The manual clearly warns that the feature used to be broken. — Álvaro González, Apr 30 '18 at 06:52
The use of -1 is on the manual page - http://php.net/manual/en/function.imagescale.php — Nigel Ren, Apr 30 '18 at 07:05
You don't need to know the aspect ratio of the input image in advance. But you certainly know the maximum dimensions of the resized image and this is enough to compute the actual dimensions of the resized image for a given input image. — axiac, Apr 30 '18 at 07:07
@ÁlvaroGonzález, I tried `-1` - doesn't work. Resulting image is a black square 160 x 160 — qadenza, Apr 30 '18 at 07:12
@axiac, I don't have max but strictly `160` value. You just need to say - how to compute another dimension. — qadenza, Apr 30 '18 at 07:22
You cannot resize to `160x160` **and** preserve the aspect ratio on the same time if the input image is not a square. You probably want to preserve the aspect ratio and resize the image to fit in a `160x160` square. — axiac, Apr 30 '18 at 07:48
@axiac, and my question is - how to get another dimension if one dimesnion is `160`? — qadenza, Apr 30 '18 at 07:58
You have plenty of examples in the answers of this question and in the answers of the duplicate. — axiac, Apr 30 '18 at 12:21

d.coder · Answer 1 · 2018-04-30T07:28:25.053

First of all you will have to mention al-least one dimension (either height or width) then using aspect ration of original image you can identify another. Here is a sample code which i used in my case:

$width = 160; // User-defined
$height = ''; // User-defined

$path = $uploadDir . '/' . $tempname;
$mime = getimagesize($path);

// Load original image
if($mime['mime']=='image/png') { 
    $orig_img = imagecreatefrompng($path);
}
if($mime['mime']=='image/jpg' || $mime['mime']=='image/jpeg' ||     $mime['mime']=='image/pjpeg') {
    $orig_img = imagecreatefromjpeg($path);
}   

// Get original image height and width
$width_orig = imagesx($orig_img);
$height_orig = imagesy($orig_img);

// Aspect ratio of original image
$aspectRatio = $width_orig / $height_orig;

// If any one dimension available then calculate other with the help of aspect-ratio of original image
if ($width == '' && $height != '') {
    $newheight = $height;
    $newwidth =  round($height * $aspectRatio);
}
if ($width != '' && $height == '') {
    $newheight = round($width / $aspectRatio);
    $newwidth = $width;
}

$newimg = imagescale($orig_img, $newwidth, $newheight, IMG_BICUBIC);

On top of everything, by what size (either height or width but at-least one required) you want to scale image... — d.coder, Apr 30 '18 at 07:29

Joseph_J · Accepted Answer · 2018-05-01T06:57:11.583

I made a function that will do what you need. I have tested this function with scaling down images and it works as intended.

This function will size an image preserving the aspect ratio to completely fit inside the dimensions that you specify. The image will also be centered.

The function also has the ability to crop. If you use the crop parameter, it will oversize the image to make sure the smallest side of the image fills the desired dimensions. It will then crop the image to fit inside the dimensions, thus completely filling the given dimensions. The image will be centered.

Here is the function:

function scaleMyImage($filePath, $newPath, $newSize, $crop = NULL){

  $img = imagecreatefromstring(file_get_contents($filePath));

  $dst_x = 0;
  $dst_y = 0;

  $width   = imagesx($img);
  $height  = imagesy($img);

  $newWidth   = $newSize;
  $newHeight  = $newSize;

  if($width < $height){  //Portrait.

    if($crop){

      $newWidth   = floor($width * ($newSize / $width));
      $newHeight  = floor($height * ($newSize / $width));
      $dst_y = (floor(($newHeight - $newSize)/2)) * -1;

    }else{

      $newWidth = floor($width * ($newSize / $height));
      $newHeight = $newSize;
      $dst_x = floor(($newSize - $newWidth)/2);

      }


  } elseif($width > $height) {  //Landscape


    if($crop){

      $newWidth   = floor($width * ($newSize / $height));
      $newHeight  = floor($height * ($newSize / $height));
      $dst_x = (floor(($newWidth - $newSize)/2)) * -1;


    }else{

      $newWidth = $newSize;
      $newHeight = floor($height * ($newSize / $width));
      $dst_y = floor(($newSize - $newHeight)/2);

      }


    }

  $finalImage = imagecreatetruecolor($newSize, $newSize);

  imagecopyresampled($finalImage, $img, $dst_x, $dst_y, 0, 0, $newWidth, $newHeight, $width, $height);

  imagejpeg($finalImage, $newPath, 60);  //Set your compression.

  imagedestroy($img);
  imagedestroy($finalImage);

}

How to use:

$newSize = 160;
$filePath = 'path/myImg.jpg';
$newPath = 'path/newImg.jpg';
$crop = 1;  //Set to NULL if you don't want to crop.

scaleMyImage($filePath, $newPath, $newSize, 1);

This should do exactly what you want with the crop parameter set to 1.

you copied this code from somewhere, that's from totally different scenario. — qadenza, Apr 30 '18 at 07:56
Why the down vote? You set the desired width and this will scale your image. I have adapted this very code and incorporated it into a class for my own site. It works great. I just put in the basics here in this function to show you how it works. Maybe I'm completely missing your question. Did you run it? It will do what you want. — Joseph_J, Apr 30 '18 at 08:02
My question is - how to calculate `width` if `height` is `160` or vice versa ? — qadenza, Apr 30 '18 at 08:09
Any. For example - original is `1600 x 950` and need to scale width to `250`. How to calculate new height? — qadenza, Apr 30 '18 at 08:16
This is how you calculate the new height.. $newHeight = floor(950 * (250 / 1600)); — Joseph_J, Apr 30 '18 at 08:18
This is how you calculate the width if you want .. $newWidth = floor(1600 * (250 / 950)); — Joseph_J, Apr 30 '18 at 08:20
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/170067/discussion-between-joseph-j-and-bonaca). — Joseph_J, Apr 30 '18 at 08:21
@bonaca Check my updated answer. It should do exactly what you want. Cheers! — Joseph_J, May 01 '18 at 06:58

scale an image proportionally without knowing both dimensions

2 Answers2