image compression in php - php

Question

I am compressing an image using following class..
<?php
class SimpleImage {
var $image;
var $image_type;
function load($filename) {
$image_info = getimagesize($filename);
$this->image_type = $image_info[2];
if( $this->image_type == IMAGETYPE_JPEG ) {
$this->image = imagecreatefromjpeg($filename);
} elseif( $this->image_type == IMAGETYPE_GIF ) {
$this->image = imagecreatefromgif($filename);
} elseif( $this->image_type == IMAGETYPE_PNG ) {
$this->image = imagecreatefrompng($filename);
}
}
function save($filename,$image_type=IMAGETYPE_JPEG,$compression=75,$permissions=null){
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image,$filename,$compression);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image,$filename);
} elseif( $image_type == IMAGETYPE_PNG ) {
imagepng($this->image,$filename);
}
if( $permissions != null) {
chmod($filename,$permissions);
}
}
function output($image_type=IMAGETYPE_JPEG) {
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image);
} elseif( $image_type == IMAGETYPE_PNG ) {
imagepng($this->image);
}
}
function getWidth() {
return imagesx($this->image);
}
function getHeight() {
return imagesy($this->image);
}
function resizeToHeight($height) {
$ratio = $height / $this->getHeight();
$width = $this->getWidth() * $ratio;
$this->resize($width,$height);
}
function resizeToWidth($width) {
$ratio = $width / $this->getWidth();
$height = $this->getheight() * $ratio;
$this->resize($width,$height);
}
function scale($scale) {
$width = $this->getWidth() * $scale/100;
$height = $this->getheight() * $scale/100;
$this->resize($width,$height);
}
function resize($width,$height) {
$new_image = imagecreatetruecolor($width, $height);
imagecopyresampled($new_image,$this->image,0,0,0,0,$width,$height,$this->getWidth(),$this->getHeight());
$this->image = $new_image;
}
}
?>
And my php code looks like..
include_once(ROOT.'/library/SimpleImage.php')
$image = new SimpleImage();
$image->load($image_name);
$image->resizeToWidth(100);
$image->save($image_name);
Now the problem is that my images are getting compressed, but their original color combination get lost...
Don't know what to do..??
Please suggest another class for image compression.

Answer 1

This is a function I coded a long time ago, it's not realy optimized but it should do the trick. Works for various mime types and allows you to save the modified image into a new location. You can easily simplify it if you need less features.
public function resizePicture($path, $new_path, $new_width, $new_height, $proportion = false) {
$size = getimagesize($path);
$x = 0;
$y = 0;
switch($size['mime']) {
case 'image/jpeg':
$picture = imagecreatefromjpeg($path);
break;
case 'image/png':
$picture = imagecreatefrompng($path);
break;
case 'image/gif':
$picture = imagecreatefromgif($path);
break;
default:
return false;
break;
}
$width = $size[0];
$height = $size[1];
$frame = imagecreatetruecolor($new_width, $new_height);
if($size['mime'] == 'image/jpeg') {
$bg = imagecolorallocate($frame, 255, 255, 255);
imagefill($frame, 0, 0, $bg);
} else if($size['mime'] == 'image/gif' or $size['mime'] == 'image/png') {
imagealphablending($picture, false);
imagesavealpha($picture, true);
imagealphablending($frame, false);
imagesavealpha($frame, true);
}
if($width < $new_width and $height < $new_height) {
$x = ($new_width - $width) / 2;
$y = ($new_height - $height) / 2;
imagecopy($frame, $picture, $x, $y, 0, 0, $width, $height);
} else {
if($proportion and $width != $height) {
if($width > $height) {
$old_height = $new_height;
$new_height = $height * $new_width / $width;
$y = abs($old_height - $new_height) / 2;
} else {
$old_width = $new_width;
$new_width = $width * $new_height / $height;
$x = abs($old_width - $new_width) / 2;
}
}
imagecopyresampled($frame, $picture, $x, $y, 0, 0, $new_width, $new_height, $width, $height);
}
switch($size['mime']) {
case 'image/jpeg':
imagejpeg($frame, $new_path, 85);
break;
case 'image/png':
imagepng($frame, $new_path, 8);
break;
case 'image/gif':
imagegif($frame, $new_path);
break;
default:
return false;
break;
}
}

Answer 2

I use SimpleImage.php and find it a helpful little script, but I had to change the value of $compression to 100 in save function.
Perhaps compressing certain formats reduces number of colors, but by setting $compression to a 100 you tell the script "Don't compress!"
After that the images look like they suppose to.