Scale Image Using PHP and Maintaining Aspect Ratio
Solution 1:
Actually the accepted solution it is not the correct solution. The reason is simple: there will be cases when the ratio of the source image and the ratio of the destination image will be different. Any calculation should reflect this difference.
Please note the relevant lines from the example given on PHP.net website:
$ratio_orig = $width_orig/$height_orig;
if ($width/$height > $ratio_orig) {
$width = $height*$ratio_orig;
} else {
$height = $width/$ratio_orig;
}
The full example may be found here: http://php.net/manual/en/function.imagecopyresampled.php
There are other answers (with examples) on stackoverflow to similar questions (the same question formulated in a different manner) that suffer of the same problem.
Example:
Let's say we have an image of 1630 x 2400 pixels that we want to be auto resized keeping the aspect ratio to 160 x 240. Let's do some math taking the accepted solution:
if($old_x < $old_y)
{
$thumb_w = $old_x*($new_width/$old_y);
$thumb_h = $new_height;
}
height = 240 width = 1630 * ( 160/2400 ) = 1630 * 0.0666666666666667 = 108.6666666666667 108.6 x 240 it's not the correct solution.
The next solution proposed is the following:
if($old_x < $old_y)
{
$thumb_w = $old_x/$old_y*$newHeight;
$thumb_h = $newHeight;
}
height = 240; width = 1630 / 2400 * 240 = 163 It is better (as it maintain the aspect ratio), but it exceeded the maximum accepted width.
Both fail.
We do the math according to the solution proposed by PHP.net: width = 160 height = 160/(1630 / 2400) = 160/0.6791666666666667 = 235.5828220858896 (the else clause). 160 x 236 (rounded) is the correct answer.
Solution 2:
I had written a peice of code like this for another project I've done. I've copied it below, might need a bit of tinkering! (It does required the GD library)
These are the parameters it needs:
$image_name - Name of the image which is uploaded
$new_width - Width of the resized photo (maximum)
$new_height - Height of the resized photo (maximum)
$uploadDir - Directory of the original image
$moveToDir - Directory to save the resized image
It will scale down or up an image to the maximum width or height
function createThumbnail($image_name,$new_width,$new_height,$uploadDir,$moveToDir)
{
$path = $uploadDir . '/' . $image_name;
$mime = getimagesize($path);
if($mime['mime']=='image/png') {
$src_img = imagecreatefrompng($path);
}
if($mime['mime']=='image/jpg' || $mime['mime']=='image/jpeg' || $mime['mime']=='image/pjpeg') {
$src_img = imagecreatefromjpeg($path);
}
$old_x = imageSX($src_img);
$old_y = imageSY($src_img);
if($old_x > $old_y)
{
$thumb_w = $new_width;
$thumb_h = $old_y*($new_height/$old_x);
}
if($old_x < $old_y)
{
$thumb_w = $old_x*($new_width/$old_y);
$thumb_h = $new_height;
}
if($old_x == $old_y)
{
$thumb_w = $new_width;
$thumb_h = $new_height;
}
$dst_img = ImageCreateTrueColor($thumb_w,$thumb_h);
imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);
// New save location
$new_thumb_loc = $moveToDir . $image_name;
if($mime['mime']=='image/png') {
$result = imagepng($dst_img,$new_thumb_loc,8);
}
if($mime['mime']=='image/jpg' || $mime['mime']=='image/jpeg' || $mime['mime']=='image/pjpeg') {
$result = imagejpeg($dst_img,$new_thumb_loc,80);
}
imagedestroy($dst_img);
imagedestroy($src_img);
return $result;
}
Solution 3:
Formule is wrong for keeping aspect ratio. It should be: original height / original width x new width = new height
function createThumbnail($imageName,$newWidth,$newHeight,$uploadDir,$moveToDir)
{
$path = $uploadDir . '/' . $imageName;
$mime = getimagesize($path);
if($mime['mime']=='image/png'){ $src_img = imagecreatefrompng($path); }
if($mime['mime']=='image/jpg'){ $src_img = imagecreatefromjpeg($path); }
if($mime['mime']=='image/jpeg'){ $src_img = imagecreatefromjpeg($path); }
if($mime['mime']=='image/pjpeg'){ $src_img = imagecreatefromjpeg($path); }
$old_x = imageSX($src_img);
$old_y = imageSY($src_img);
if($old_x > $old_y)
{
$thumb_w = $newWidth;
$thumb_h = $old_y/$old_x*$newWidth;
}
if($old_x < $old_y)
{
$thumb_w = $old_x/$old_y*$newHeight;
$thumb_h = $newHeight;
}
if($old_x == $old_y)
{
$thumb_w = $newWidth;
$thumb_h = $newHeight;
}
$dst_img = ImageCreateTrueColor($thumb_w,$thumb_h);
imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);
// New save location
$new_thumb_loc = $moveToDir . $imageName;
if($mime['mime']=='image/png'){ $result = imagepng($dst_img,$new_thumb_loc,8); }
if($mime['mime']=='image/jpg'){ $result = imagejpeg($dst_img,$new_thumb_loc,80); }
if($mime['mime']=='image/jpeg'){ $result = imagejpeg($dst_img,$new_thumb_loc,80); }
if($mime['mime']=='image/pjpeg'){ $result = imagejpeg($dst_img,$new_thumb_loc,80); }
imagedestroy($dst_img);
imagedestroy($src_img);
return $result;
}
Solution 4:
<?php
Class ResizedImage
{
public $imgfile;
public $string = '';
public $new_width = 0;
public $new_height = 0;
public $angle = 0;
public $max_font_size = 1000;
public $cropped = false;//whether crop the original image if h or w > new h or w
public $font = 'fonts/arialbd.ttf';
private $img;
private $trans_colour;
private $orange;
private $white;
private $whitetr;
private $blacktr;
public function PrintAsBase64()
{
$this->SetImage();
ob_start();
imagepng($this->img);
$b64img = ob_get_contents();
ob_clean();
imagedestroy($this->img);
$b64img = base64_encode($b64img);
echo($b64img);
}
public function PrintAsImage()
{
$this->SetImage();
header('Content-type: image/png');
imagepng($this->img);
imagedestroy($this->img);
}
private function SetImage()
{
if ($this->imgfile == '') {$this->imgfile='NoImageAvailable.jpg';}
$this->img = imagecreatefromstring(file_get_contents($this->imgfile));
$this->trans_colour = imagecolorallocatealpha($this->img, 0, 0, 0, 127);
$this->orange = imagecolorallocate($this->img, 220, 210, 60);
$this->white = imagecolorallocate($this->img, 255,255, 255);
$this->whitetr = imagecolorallocatealpha($this->img, 255,255, 255, 95);
$this->blacktr = imagecolorallocatealpha($this->img, 0, 0, 0, 95);
if ((!$this->cropped) && ($this->string !=''))
{$this->watermarkimage();}
if (($this->new_height > 0) && ($this->new_width > 0)) {$this->ResizeImage();};
if (($this->cropped) && ($this->string !=''))
{$this->watermarkimage();}
imageAlphaBlending($this->img, true);
imageSaveAlpha($this->img, true);
}
////
private function ResizeImage()
{
# v_fact and h_fact are the factor by which the original vertical / horizontal
# image sizes should be multiplied to get the image to your target size.
$v_fact = $this->new_height / imagesy($this->img);//target_height / im_height;
$h_fact = $this->new_width / imagesx($this->img);//target_width / im_width;
# you want to resize the image by the same factor in both vertical
# and horizontal direction, so you need to pick the correct factor from
# v_fact / h_fact so that the largest (relative to target) of the new height/width
# equals the target height/width and the smallest is lower than the target.
# this is the lowest of the two factors
if($this->cropped)
{ $im_fact = max($v_fact, $h_fact); }
else
{ $im_fact = min($v_fact, $h_fact); }
$new_height = round(imagesy($this->img) * $im_fact);
$new_width = round(imagesx($this->img) * $im_fact);
$img2 = $this->img;
$this->img = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($this->img, $img2, 0, 0, 0, 0, $new_width, $new_height, imagesx($img2), imagesy($img2));
$img2 = $this->img;
$this->img = imagecreatetruecolor($this->new_width, $this->new_height);
imagefill($this->img, 0, 0, $this->trans_colour);
$dstx = 0;
$dsty = 0;
if ($this->cropped)
{
if (imagesx($this->img) < imagesx($img2))
{ $dstx = round((imagesx($this->img)-imagesx($img2))/2); }
if (imagesy($this->img) < imagesy($img2))
{ $dsty = round((imagesy($this->img)-imagesy($img2))/2); }
}
else
{
if (imagesx($this->img) > imagesx($img2))
{ $dstx = round((imagesx($this->img)-imagesx($img2))/2); }
if (imagesy($this->img) > imagesy($img2))
{ $dsty = round((imagesy($this->img)-imagesy($img2))/2); }
}
imagecopy ( $this->img, $img2, $dstx, $dsty, 0, 0, imagesx($img2) , imagesy($img2));
imagedestroy($img2);
}
////
private function calculateTextBox($text,$fontFile,$fontSize,$fontAngle)
{
/************
simple function that calculates the *exact* bounding box (single pixel precision).
The function returns an associative array with these keys:
left, top: coordinates you will pass to imagettftext
width, height: dimension of the image you have to create
*************/
$rect = imagettfbbox($fontSize,$fontAngle,$fontFile,$text);
$minX = min(array($rect[0],$rect[2],$rect[4],$rect[6]));
$maxX = max(array($rect[0],$rect[2],$rect[4],$rect[6]));
$minY = min(array($rect[1],$rect[3],$rect[5],$rect[7]));
$maxY = max(array($rect[1],$rect[3],$rect[5],$rect[7]));
return array(
"left" => abs($minX) - 1,
"top" => abs($minY) - 1,
"width" => $maxX - $minX,
"height" => $maxY - $minY,
"box" => $rect );
}
private function watermarkimage($font_size=0)
{
if ($this->string == '')
{die('Watermark function call width empty string!');}
$box = $this->calculateTextBox($this->string, $this->font, $font_size, $this->angle);
while ( ($box['width'] < imagesx($this->img)) && ($box['height'] < imagesy($this->img)) && ($font_size <= $this->max_font_size) )
{
$font_size++;
$box = $this->calculateTextBox($this->string, $this->font, $font_size, $this->angle);
}
$font_size--;
$box = $this->calculateTextBox($this->string, $this->font, $font_size, $this->angle);
$vcenter = round((imagesy($this->img) / 2) + ($box['height'] / 2));
$hcenter = round((imagesx($this->img) - $box['width']) / 2 );
imagettftext($this->img, $font_size, $this->angle, $hcenter, $vcenter, $this->blacktr, $this->font, $this->string);
imagettftext($this->img, $font_size, $this->angle, $hcenter+1, $vcenter-2, $this->whitetr, $this->font, $this->string);
}
}
?>
Also I have been using the accepted answer but it does not keep the ratio in some cases. I have found some good answers on the forum and have put them in together and finally created a Class which resizes an image. As extra function u can put a watermark text.
u can see what happens when choose to crop or not, if not a transparent area will be added to the new resized image.
This example is more than asked, but I think it is a good example.