Images in PHP

Napalm Llama · 04-05-2005, 06:08 AM

Hi. I need to know how to resize an image in a PHP script. It only has to go smaller. Unfortunately, I can't seem to find anythinga bout it either in my PHP book or in the online documentation.

A function that does it for you would be great, but I'm prepared to code it myself, if somebody would just tell me where to start...

Im thinking "In the case of an image that's 3 times too big, read every third line of that image and put it into a new one. Then read every third column of that image, and put it into the final one."

So you see it doesn't have to be pretty (although pretty would be nice) - it just has to work.

Any ideas?

[edit]
I guess to make it pretty, I'd have to say "look at every block of nine pixels, take the average colour, and write that as a new pixel in the final image"... but I don't know how to do that either

marghorp · 04-05-2005, 06:27 AM

You need the GD2 libraries enabled. I can give you a sample code when I get home.

Searched for it for quite some time.

Napalm Llama · 04-05-2005, 06:36 AM

I think GD is there.

Looks like there actually is a function to do it in PHP, though, and it looks like this:
imagecopyresampled ( resource dst_image, resource src_image, int dst_x, int dst_y, int src_x, int src_y, int dst_w, int dst_h, int src_w, int src_h )

Well, looks like I'm going to have fun working that one out

deiussum · 04-05-2005, 08:41 AM

Here's a thumbnailing function I wrote in PHP quite awhile ago. Should give you a good start, though. This particular one resizes it so that the width is always 100, and the height of the thumbnail is the same approximate ratio as the original.

PHP Code:



function MakeThumb($src, $dest) 
{ 
    $img = imagecreatefromjpeg($src); 
 
    if ($img) { 
 
        $imginfo = getimagesize($src); 
        $w = $imginfo[0]; 
        $h = $imginfo[1]; 
 
        $w1 = 100; 
        $h1 = $w1 * $h / $w; 
        $thumb = imagecreate($w1, $h1); 
 
        if (ImageCopyResized($thumb, $img, 0, 0, 0, 0, $w1, $h1, $w, $h)) { 
            if (ImageJPEG($thumb, $dest)) { 
                return 1; 
            } 
            else { 
                return 0; 
            } 
        } 
        else { 
            return 0; 
        } 
    } 
    else { 
        return 0; 
    } 
}

Napalm Llama · 04-05-2005, 11:01 AM

Woo! Thanks

Hmm, I should have said this a couple of hours ago...
I've actually figured out how to do it myself

PHP Code:



<?php 
 
$xlim = 300;    // Maximum width 
$ylim = 150;    // Maximum height 
$hi_q = false;    // Do resampling? 
 
$file = $_REQUEST["file"]; 
include("functions.php"); 
 
// Check whether it really is an image 
if( !isimg($file) ) { 
    die("bad image"); 
} 
 
// Decide which image type we're working with 
switch( isimg($file) ) { 
    case "jpg": 
        $orig = imagecreatefromjpeg( $file ); 
        header('Content-type: image/jpeg'); 
        imagejpeg(resize($orig)); 
        break; 
     
    case "jpeg": 
        $orig = imagecreatefromjpeg( $file ); 
        header('Content-type: image/jpeg'); 
        imagejpeg(resize($orig)); 
        break; 
     
    case "gif": 
        $orig = imagecreatefromgif( $file ); 
        header('Content-type: image/gif'); 
        imagegif(resize($orig)); 
        break; 
     
    case "png": 
        $orig = imagecreatefrompng( $file ); 
        header('Content-type: image/png'); 
        imagepng(resize($orig)); 
        break; 
} 
 
// Does all the non image-type specific bits 
function resize( $imgin ) { 
     
    // Import globals 
    global $xlim, $ylim, $hi_q; 
     
    // Get the current sizes 
    $ox = imagesx( $imgin ); 
    $oy = imagesy( $imgin ); 
     
    // Get the percentage change from old to potential new 
    $xdiff = $xlim / ( $ox/100 ); 
    $ydiff = $ylim / ( $oy/100 ); 
     
    // If new image is larger than old, just use old 
    if( $xdiff > 100 && $ydiff > 100 ) { 
        return $imgin; 
    } 
     
    // Decide which dimension is the most oversized, and calculate ratio from that 
    if( $xdiff > $ydiff ) { 
        $ratio = $ydiff/100; 
    } else { 
        $ratio = $xdiff/100; 
    } 
     
    // Calculate the new dimensions 
    $nx = $ox * $ratio; 
    $ny = $oy * $ratio; 
     
    // Make a new canvas for the output image 
    $imgout = imagecreatetruecolor( $nx, $ny ); 
     
    // Shrink old image and copy to new canvas 
    if( $hi_q ) { 
        imagecopyresampled($imgout, $imgin, 0, 0, 0, 0, $nx, $ny, $ox, $oy); 
    } else { 
        imagecopyresized($imgout, $imgin, 0, 0, 0, 0, $nx, $ny, $ox, $oy); 
    } 
     
    // Send shrunken image back to the caller 
    return $imgout; 
     
} 
 
?>

All you need in addition is a functions.php containing this:

PHP Code:



function isimg($name) { 
    $file_exts = explode(".",$name); 
    $ext = count($file_exts) - 1; 
    $ext = strtolower($file_exts[$ext]); 
    if ( $ext == "jpg" || $ext == "jpeg" || $ext == "gif" || $ext == "png" ) { 
        return $ext; 
    } else { 
        return false; 
    } 
}

And you're set. You use it like this:

Code:

<img src="img.php?file=bigpicture.jpg" alt="Thumbnail of BigPicture">

What do you think?
I'm working on a caching thingy at the moment, so it doesn't hog so much CPU time.

It's being used as part of the project described in my sig, which is why it has to refer out to the functions.php file.
At the moment all the application does as a whole is let you browse your file tree remotely, and execute shell commands as 'nobody'.
I'm going to add caching though, because if I'm browsing my pictures directory, all those thumbnails take quite a while to generate...

Napalm Llama · 04-06-2005, 08:17 AM

Yay! A release!

If anybody passed by yesterday and was interested in this, they can now take it for a test drive...

www.yellowmackerel.co.uk/os/phpfinder.htm