Resize image without lose quality when image is bigger - php

Question

I use img uploader on my ftp.
If image large to 1024x768 i use script for resize.
But after resize lose quality.
Code from uploader.php:
if(#move_uploaded_file($_FILES['myfile']['tmp_name'], "$upload_folder/" . $newname))
if($width>1024 || $height>768) {
require './image_resize.php';
echo (image_resize("$upload_folder/" . $newname, "$upload_folder/" . $newname, 1024, 768));
}
Code prom image_resize.php:
<?php ini_set('memory_limit','500M');
function image_resize($src, $dst, $width, $height, $crop=0){
if(!($pic = #getimagesize($src)))
return false;
$w = $pic[0];
$h = $pic[1];
$type = substr($pic['mime'], 6);
$func = 'imagecreatefrom' . $type;
if(!function_exists($func))
return false;
$img = $func($src);
if($crop){
if($w < $width && $h < $height)
return false;
$ratio = max($width/$w, $height/$h);
$h = $height / $ratio;
$x = ($w - $width / $ratio) / 2;
$w = $width / $ratio;
}
else{
if($w < $width && $h < $height)
return false;
$ratio = min($width/$w, $height/$h);
$width = $w * $ratio;
$height = $h * $ratio;
$x = 0;
}
$new = imagecreatetruecolor($width, $height);
if($type == "gif" || $type == "png"){
imagecolortransparent($new, imagecolorallocatealpha($new, 0, 0, 0, 127));
imagealphablending($new, false);
imagesavealpha($new, true);
}
imagecopyresampled($new, $img, 0, 0, $x, 0, $width, $height, $w, $h);
$save = 'image' . $type;
$save($new, $dst);
return true;
}
It is impossible to reduce the size without losing quality :(

Answer 1

I found script for resize, working fine. I think this is a what I need :)
http://sanchiz.net/blog/resizing-images-with-php
But, one problem and please correct for me: If need resize PNG with transparent background this script remove transparent and add black background.
In comments posted modified script, but with this code not working compress function
I need modify this code for resize PNG without remove transparent background:
class SimpleImage {
public $image;
public $image_type;
public function load($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);
}
}
public function save($filename, $image_type = IMAGETYPE_JPEG, $compression = 100, $permissions = NULL) {
if ($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, $permissions);
}
}
public function output($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);
}
}
public function resizeToHeight($height) {
$ratio = $height / $this->getHeight();
$width = $this->getWidth() * $ratio;
$this->resize($width, $height);
}
public function getHeight() {
return imagesy($this->image);
}
public function getWidth() {
return imagesx($this->image);
}
public function resize($width, $height) {
$new_image = imagecreatetruecolor($width, $height);
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $new_image;
}
public function resizeToWidth($width) {
$ratio = $width / $this->getWidth();
$height = $this->getheight() * $ratio;
$this->resize($width, $height);
}
public function scale($scale) {
$width = $this->getWidth() * $scale / 100;
$height = $this->getheight() * $scale / 100;
$this->resize($width, $height);
}
Thank you

Answer 2

Since the default API may not be really effective when it comes to image handling, i suggest you use a library. Take a look at grafika

Answer 3

You can also use an external service for images resizing such as this repo
Flyimg.