Image Resizing

[ThaSpY]

This niftly little function I wrote uses [man]getimagesize/man to create a nice little thumbnail of an image while keeping the aspect ratio. It does not store the new image, but merely sets the dimensions for the <img> tag. Any suggestions or concerns with this code?

function imageresize($max_width,$max_height,$image){

$dimensions=getimagesize($image);

$width_percentage=$max_width/$dimensions[0];
$height_percentage=$max_height/$dimensions[1];

if($width_percentage <= $height_percentage){
	$new_width=$width_percentage*$dimensions[0];
	$new_height=$width_percentage*$dimensions[1];
}else{
	$new_width=$height_percentage*$dimensions[0];
	$new_height=$height_percentage*$dimensions[1];
}

$new_image=array($new_width,$new_height);
return $new_image;
}

$dimensions=imageresize("100","250","images/blog.gif");

$image="<img src='images/blog.gif' width='$dimensions[0]' height='$dimensions[1]'>";

?>

[Weedpacket]

I'd use round() or similar so that nonintegral sizes don't get used.

But then, I don't like making "thumbnails" out of full-sized images by just using smaller image dimensions. There's no saving for anyone anywhere except screen real estate.

[ThaSpY]

Thank you, I will impliment the [man]round/man.

Originally I looked at creating a whole new image and storing it, but that was a little over my head, so I went with the latter for simplicity's sake.

[jebster]

Originally posted by ThaSpY
Thank you, I will impliment the [man]round/man.

Originally I looked at creating a whole new image and storing it, but that was a little over my head, so I went with the latter for simplicity's sake.

It's actually surprisingly simple [man]imagecreatefromjpeg[/man] [man]imagecreatetruecolor[/man] [man]imagecopyresized[/man] [man]imagejpeg[/man] [man]imagedestroy[/man] or something like that.. and say you want to make the thumbnails greyscale, Weedpacket posted a nice little example here: http://www.phpbuilder.com/board/showthread.php?postid=10479545#post10479545

[Phfeenikz]

Try this one, it creates the thumbs and saves them to a file. Resizing the image in the img tag is a bad idea and you really should create a seperate thumb image. Keep in mind that when using this to resize multiple images, runtime can be rather lengthy since the image functions seem to be very resource intensive

<?php
/*
mkthumb() function.  05/15/2004

Parameters:
	$dirname - Path of the source photo.
	$filename - Filename of source photo, which will also be used to create the thumb.
	$thumbdir - Path to save the thumb to. Must be different than $dirname.
	$thumb_size - Desired size of the longest side of the thumb in pixels. Default is 120.

ex:
	$img_path = '../img_path';
	$img_name = 'img.jpg';
	$thumb_path = '../thumb_path';
	$size = 100;

mkthumb($img_path, $img_name, $thumb_path, $size);
*/

function mkthumb($dirname, $filename, $thumbdir, $thumb_size = 120)
{
	if (isset($filename))
	{
		//get filetype and check to make sure it is an accepable image. if gif, jpeg, or png create
		//source image.
		$imtype = exif_imagetype($dirname.$filename);

	switch($imtype)
	{
		case 1 : //Image is type gif.
			$im = imagecreatefromgif($dirname.$filename);
			break;
		case 2 : //Image is type jpeg.
			$im = imagecreatefromjpeg($dirname.$filename);
			break;
		case 3 : //Image is png.
			$im = imagecreatefrompng($dirname.$filename);
			break;
		default : //File not accepted.
			echo "Error: $filename is an invalid file.<br>";
			break;
	}

	if (isset($im)) 
	{
		//get width of source photo.
		$width = ImageSX($im);
		$height = ImageSY($im);

		//set aspect ratio so that the thumb is not distorted.
		if ($width < $height)
		{
			$asp_ratio = $thumb_size/$height;
		}
		else
		{
			$asp_ratio = $thumb_size/$width;
		}

		//calculate thumb width using aspect ratio percetage.
		$thumb_width = round(($width * $asp_ratio));
		$thumb_height = round(($height * $asp_ratio));

		//create thumb image.
		$im_thumb = imagecreatetruecolor($thumb_width, $thumb_height);

		//resize and copy source image to the thumb image.
		imagecopyresampled($im_thumb, $im, 0, 0, 0, 0, $thumb_width, $thumb_height, $width,$height);

		//create 
		switch($imtype)
		{
			case 1 : //Image is type gif.
				$im_new = imagegif($im_thumb,$thumbdir.$filename);
				break;
			case 2 : //Image is type jpeg.
				$im_new = imagejpeg($im_thumb,$thumbdir.$filename);
				break;
			case 3 : //Image is png.
				$im_new = imagepng($im_thumb,$thumbdir.$filename);
				break;
			default :
				$im_new = imagejpeg($im_thumb,$thumbdir.$filename);
				break;
		}	
		imagedestroy($im);
		imagedestroy($im_thumb);
	}
	else
	{
		echo "Error: Cannot process image<br>";
		return false;
	}
}
else
{
	echo "Error: Filename required<br>";
	return false;
}
echo "Created thumb $thumbdir$filename<br>";
return true;
}

?>

[jebster]

Note that, that will not work with GIF's if the person is using GD 1.6 or later.

[zapa]

Not sure were i took this from but i love it!

I use it to resize Images without saving them, also good for showing thmubnails of big image.

also will keep aspect,
use it in your IMG SRC tag
like so
<IMG SRC="tn_image.php?image=file.jpg">

<?php
// make thmubnail of image
function sizeImage($image, $x, $y, $proportional) {
if (!$attr = getimagesize($image)) {
trigger_error("GD: Image does not exist. Must be gif, jpeg, or png!",E_USER_ERROR);
}

switch ($attr[2]) {
case 1:
$image = imagecreatefromgif($image);
break;
case 2:
$image = imagecreatefromjpeg($image);
break;
case 3:
$image = imagecreatefrompng($image);
break;
default:
trigger_error("GD: Image type wrong. Must be gif, jpeg, or png!", E_USER_ERROR);
}
if ($proportional) {
if ($attr[0]<$attr[1]){
$x = $y * ($attr[0]/$attr[1]);
}
else{
$y = $x / ($attr[0]/$attr[1]);
} 
}
$newimage = imagecreatetruecolor($x,$y);
imagecopyresampled($newimage, $image, 0, 0, 0, 0, $x, $y, $attr[0], $attr[1]);
imagepng($newimage);
imagedestroy($image);
imagedestroy($newimage);
}
$image = $_GET['image']; //image location
$x = 150; //width
$y = 100; //height
$proportional = TRUE; //proportional or not
header("Content-type: image/png"); //so we can use the image right in a tag. <img src="image.php?image=me.gif">
sizeImage($image, $x, $y, $proportional);
?>

[quaTTro]

Hello guys. I´ve downloaded this code from the site but can´t work out why does it make so dirty thumbnails. They are coloured, or just bad. I´ll show you an example if you want. Well, the code is:

<?$maxw = 150; // maximum width of images (height will be scaled accordingly)
$thumbdir = "thumbs"; // directory to place thumbnail images
$url = $_SERVER["PHP_SELF"]."?";
$sfxs = array(".jpg",".jpeg",".png",".JPG");
$curdir = dirname(stripslashes($_SERVER["PATH_TRANSLATED"]));
$slash = (strstr($curdir,"\\") ) ? "\\" : "/";
$thumbdir = $thumbdir;
$images = array();
@ $handle = opendir($curdir);
if (!$handle ) {
	error("could not open directory!");
	exit;
}

while ( $file = readdir($handle) ) {
	if (isValid($file,$sfxs) ) {
		$tmp = array();
		$tmp[0] = $file;
		$tmp[1] = filemtime($file);
		$tmp[2] = filesize($file);
		array_push($images,$tmp);
		// do we need to create a thumbnail?
		if ( !file_exists($thumbdir.$slash.$file) ) {
			createThumb($file);
		}
	}
}

function isValid($f,$a) {
	$t = getSuffix($f);
	return ( in_array($t,$a) ) ? true : false;
}
function getSuffix($f) {
	$n = strrpos($f,".");
	return substr($f,$n,strlen($f)-$n);
}
function createThumb($f) {
	// use max width config value
	global $maxw, $curdir, $copyfile, $thumbdir, $slash;
	$type = getSuffix($f);
	// png or jpeg?
	// either way get image
	if ($type==".png") {
		$input = imagecreatefrompng($f);
	} else {
		$input = imagecreatefromjpeg($f);
	}
	if ( !$input ) {
		error("not a valid image file :(");
		return false;
	}
	// get size ( [0]=width, [1]=height )
	$tmp = getimagesize($f);
	if ( !$tmp ) {
		error("Could not get input image size");
		return false;
	}
	// get width of new thumbnail by taking
	// the smaller value from max and tmp width
	$w = ($tmp[0]>$maxw) ? $maxw : $tmp[0];
	// scale height according to width
	$h = $tmp[1] * ($maxw/$tmp[0]);
	// create output image
	@ $output = imagecreate($w,$h);
	if ( !$output ) {
		error("could not create output image");
		return false;
	}
	// copy big image over to thumbnail, and resize down
	imagecopyresampled( $output,$input, 0,0, 0,0, $w,$h, $tmp[0],$tmp[1] );
	$newfile = $thumbdir.$slash.$f;
	// do the outputting!
	if ( $type == ".png" ) {
		imagepng($output,$newfile);
	} else {
		imagejpeg($output,$newfile);
	}
}
function error($str) {
	echo '<div style="background-color:#ffffff;color:#660000;font-weight:bold">'.$str.'</div>';
}
?>

Any ideas? Thanks in advance!

Edit: changed resized to resampled.

[BuzzLY]

use imagecopyresampled() instead of imagecopyresized().

[quaTTro]

It didn´t work, BuzzLY. Thanks anyway. 🙂

[BuzzLY]

Post your original and thumbnail images. And what do you mean "it didn't work?" The command doesn't work, or it didn't help the quality?

Try using imagecreatetruecolor() instead of imagecreate().

[quaTTro]

Sorry, by didn´t work I meant it didn´t change anything! So the images keep doing that, I´ll show you:
or

I didn´t change to imagecreatetruecolor yet, anyway I don´t use pngs.

If it helps you can test in http://roscorgal.com.ar/test/users/, where you can upload images and it resizes it and shows the small image.

Thanks again!

[BuzzLY]

imagecreate() creates a palette-based image. You need to use imagecreatetruecolor(). Replace this line:

[FONT=courier new]@ $output = imagecreate($w,$h);[/FONT]

with this:

[FONT=courier new]@ $output = imagecreatetruecolor($w,$h);[/FONT]

[quaTTro]

Originally posted by BuzzLY
imagecreate() creates a palette-based image. You need to use imagecreatetruecolor(). Replace this line:

[FONT=courier new]@ $output = imagecreate($w,$h);[/FONT]

with this:

[FONT=courier new]@ $output = imagecreatetruecolor($w,$h);[/FONT]

It was EXACTLY that. Thanks a lot, BuzzLY! Now everything works fine. So, solved.

If I thought it didn´t work it was because it showed my caché files instead of the new ones.