Trying to generate proportionally cropped thumbnails at a fixed width/height with PHP GD

Question

I'm trying to create a Thumbnail Generator in PHP with GD that will take an image and reduce it to a fixed width/height. The square it takes from the original image (based on my fixed width/height) will come from the center of the image to give a proportionally correct thumbnail.

I'll try to demonstrate that confusing sentence with some nice ASCII :}

LANDSCAPE EXAMPLE:

XXXXXXXXXXXXXXXX
XXXXOOOOOOOOXXXX
XXXXOOOOOOOOXXXX
XXXXOOOOOOOOXXXX
XXXXOOOOOOOOXXXX
XXXXXXXXXXXXXXXX

    XXXXXXXX    
    XXXXXXXX    
    XXXXXXXX    
    XXXXXXXX    


PORTRAIT EXAMPLE:

    XXXXXXXX
    XXXXXXXX
    OOOOOOOO
    OOOOOOOO
    OOOOOOOO
    OOOOOOOO
    XXXXXXXX
    XXXXXXXX

    XXXXXXXX    
    XXXXXXXX    
    XXXXXXXX    
    XXXXXXXX

As you can see, it pulls out a square from the center of the image to use as a thumbnail. It seems simple, in theory, to get the height/width of the image and then calculate the offset based on my fixed width/height to get the thumbnail. But I can't seem to think of a way to code it :/

Also, how would I go about resizing the image before pulling out the center square? So the thumbnail contains a detailed image of the original rather than some zoomed in graphic?

Answer 1

I'm sorry if I'm offering an indirect answer. But you could try using this library: PHPThumb. It's very easy to use. It supports GD and has this function called adaptive resizing which resizes the image from the center.

Here's a sample code from the docs for adaptive resizing:

<?php

require_once 'path/to/ThumbLib.inc.php';

try
{
     $thumb = PhpThumbFactory::create('/path/to/image.jpg');
}
catch (Exception $e)
{
     // handle error here however you'd like
}

$thumb->adaptiveResize(175, 175);
$thumb->show();

?>

Answer 2

Without a clear and well-defined goal, it is hard to try and offer a well-suited solution. Also, you will tend to find other Stackers more helpful if you at least bring an attempt at a solution to the table.

That being said, I have found a couple of tutorials online which may at least give you an idea to start with - give it a go, and, if you still have troubles, feel free to post further questions (with code samples and details of what is not behaving itself).

• Cropping with GD
• Create cropped thumbnails with GD Library

Answer 3

Is this what you're looking for:

Crop-To-Fit an Image Using ASP/PHP

Answer 4

How about this: It's take an image of any size and proportionately resize it down (or up) to fill a canvas of any dimensions.

E.g. Source image is: 400w x 600h and thumbnail size needs to be 100w x 225h - the output image will be 100w x 225h and the images will be vertically centered with a width of 100 (the maximum) and height 150 (with a top and bottom border of 37.5 pixels)

Here's the function

function resize_to_canvas($filename,$canvas_w=100,$canvas_h=225){
list($width, $height, $type) = getimagesize($filename);

$original_overcanvas_w = $width/$canvas_w;
$original_overcanvas_h = $height/$canvas_h;

$dst_w = round($width/max($original_overcanvas_w,$original_overcanvas_h),0);
$dst_h = round($height/max($original_overcanvas_w,$original_overcanvas_h),0);

$dst_image = imagecreatetruecolor($canvas_w, $canvas_h);
$background = imagecolorallocate($dst_image, 255, 255, 255);
imagefill($dst_image, 0, 0, $background);

$src_image = imagecreatefromjpeg($filename);
imagecopyresampled($dst_image, $src_image, ($canvas_w-$dst_w)/2, ($canvas_h-$dst_h)/2, 0, 0, $dst_w, $dst_h, $width, $height);
imagegif($dst_image, $filename);
imagedestroy($dst_image);}

This function will replace the original file but is easily modified to create a new thumbnail image. Just change the file name the line imagegif($dst_image, $filename);