PHP imagecopyresampled function

Like this blog? Consider exploring one of our sponsored banner ads...

imagecopyresampled

(PHP 4 >= 4.0.6, PHP 5)

imagecopyresampled() copies a rectangular
portion of one image to another image, smoothly interpolating pixel
values so that, in particular, reducing the size of an image still
retains a great deal of clarity.

If the source and destination coordinates and width and heights
differ, appropriate stretching or shrinking of the image fragment
will be performed. The coordinates refer to the upper left
corner. This function can be used to copy regions within the
same image (if dst_image is the same as
src_image) but if the regions overlap the
results will be unpredictable.

Destination image link resource

Source image link resource

x-coordinate of destination point

y-coordinate of destination point

x-coordinate of source point

y-coordinate of source point

Destination width

Destination height

Source width

Source height

Returns TRUE on success or FALSE on failure.

Example 1. Simple example

This example will resample an image to half its original size.

// The file
$filename = 'test.jpg';
$percent = 0.5;
 
// Content type
header('Content-type: image/jpeg');
 
// Get new dimensions
list($width, $height) = getimagesize($filename);
$new_width = $width * $percent;
$new_height = $height * $percent;
 
// Resample
$image_p = imagecreatetruecolor($new_width, $new_height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
 
// Output
imagejpeg($image_p, null, 100);

The above example will output
something similar to:

Example 2. Resampling an image proportionally

This example will display an image with the maximum width,
or height, of 200 pixels.

// The file
$filename = 'test.jpg';
 
// Set a maximum height and width
$width = 200;
$height = 200;
 
// Content type
header('Content-type: image/jpeg');
 
// Get new dimensions
list($width_orig, $height_orig) = getimagesize($filename);
 
$ratio_orig = $width_orig/$height_orig;
 
if ($width/$height > $ratio_orig) {
   $width = $height*$ratio_orig;
} else {
   $height = $width/$ratio_orig;
}
 
// Resample
$image_p = imagecreatetruecolor($width, $height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);
 
// Output
imagejpeg($image_p, null, 100);

The above example will output
something similar to:

Note:
There is a problem due to palette image limitations (255+1 colors).
Resampling or filtering an image commonly needs more colors than 255, a
kind of approximation is used to calculate the new resampled pixel and its
color. With a palette image we try to allocate a new color, if that
failed, we choose the closest (in theory) computed color. This is
not always the closest visual color. That may produce a weird result, like
blank (or visually blank) images. To skip this problem, please use a
truecolor image as a destination image, such as one created by
imagecreatetruecolor().

imagecopyresized()