/**
* Scale an image according to input canvas dimensions.
* No cropping will occur, the scaled image is "centered" to canvas.
*/
function imageToCanvas ($_image, $_canvasWidth, $_canvasHeight)
{
if (is_string($_image)) {
if (is_file($_image)) {
$_image = imagecreatefromjpeg($_image);
} else {
return "Incorrect imagepath >> No file here " . $_image;
}
}
$width = imagesx($_image);
$height = imagesy($_image);
$image_aspect_ratio = $width / $height;
$canvas_aspect_ratio = $_canvasWidth / $_canvasHeight;
// scale by height
if ($image_aspect_ratio < $canvas_aspect_ratio) {
$new_height = $_canvasHeight;
$new_width = ($new_height/$height) * $width;
}
// scale by width
else {
$new_width = $_canvasWidth;
$new_height = ($new_width/$width) * $height;
}
# offset values (ie. center the resized image to canvas)
$xoffset = ($_canvasWidth - $new_width) / 2;
$yoffset = ($_canvasHeight - $new_height) / 2;
$image_resized = imagecreatetruecolor($_canvasWidth, $_canvasHeight);
# fill colour
$white = imagecolorallocate($image_resized, 255, 255, 255);
imagefill($image_resized, 0, 0, $white);
imagecopyresampled($image_resized, $_image, $xoffset, $yoffset, 0, 0, $new_width, $new_height, $width, $height);
imagedestroy($_image);
return $image_resized;
}
Refactorings
No refactoring yet !
Chris Dean
August 14, 2008, August 14, 2008 07:00, permalink
I don't see any real issues with the way this works, though it all applies to GD lib - unless you're doing a check to see if GD lib's available elsewhere maybe you'd want to include something like that?
Juha Hollanti
August 14, 2008, August 14, 2008 08:11, permalink
Checking for GD lib might actually be prudent. I once lost hours trying to get something like a picture upload working on a new server. For some reason nothing gave out any error messages.
bruce
September 29, 2008, September 29, 2008 20:20, permalink
#1 problem I can see is it only accepts jpegs
Giulio Ardoino
November 18, 2010, November 18, 2010 08:55, permalink
Great function, it works very well.
James
April 14, 2011, April 14, 2011 16:15, permalink
Hi, I know this code is over 3 years old but I needed to use it in something I wrote (although I adapted it to suit). Anyway, I wanted it so that it only scaled the image down if it was too big for the canvas - otherwise it stayed the same aspect ratio (and therefore didn't risk being blurred when scaled-up). So I modified your code as below.
Note: it can be switched to always force scale (as your original code) by setting the fourth param to true.
Cheers
James
/**
* Scale an image according to input canvas dimensions.
* No cropping will occur, the scaled image is "centered" to canvas.
*/
function imageToCanvas ($_image, $_canvasWidth, $_canvasHeight, $forceScale=false)
{
if (is_string($_image)) {
if (is_file($_image)) {
$_image = imagecreatefromjpeg($_image);
} else {
return "Incorrect imagepath >> No file here " . $_image;
}
}
$width = imagesx($_image);
$height = imagesy($_image);
$image_aspect_ratio = $width / $height;
$canvas_aspect_ratio = $_canvasWidth / $_canvasHeight;
if($forceScale)
{
// scale by height
if ($image_aspect_ratio < $canvas_aspect_ratio) {
$new_height = $_canvasHeight;
$new_width = ($new_height/$height) * $width;
}
// scale by width
else {
$new_width = $_canvasWidth;
$new_height = ($new_width/$width) * $height;
}
}
else
{
if($width > $_canvasWidth)
{
$new_width = $_canvasWidth;
$new_height = ($new_width/$width) * $height;
}
elseif($height > $_canvasHeight)
{
$new_height = $_canvasHeight;
$new_width = ($new_height/$height) * $width;
}
else
{
$new_height = $height;
$new_width = $width;
}
}
# offset values (ie. center the resized image to canvas)
$xoffset = ($_canvasWidth - $new_width) / 2;
$yoffset = ($_canvasHeight - $new_height) / 2;
$image_resized = imagecreatetruecolor($_canvasWidth, $_canvasHeight);
# fill colour
$white = imagecolorallocate($image_resized, 255, 255, 255);
imagefill($image_resized, 0, 0, $white);
imagecopyresampled($image_resized, $_image, $xoffset, $yoffset, 0, 0, $new_width, $new_height, $width, $height);
imagedestroy($_image);
return $image_resized;
}
The built in image functions found in PHP manage to boggle my mind to a point where i can no longer understand anything of what's going on. I'll just end up messing around long enough to get things right.
For this reason i'm always trying to write up functions (which often end up horribly wrong) that would obfuscate all the mind boggling soup out of my sight.
Anything to make the following more bearable to live with is very, very welcome. Thanks.