imagecopyresampled -- Copy and resize part of an image with resampling
bool imagecopyresampled ( resource dst_image, resource src_image, int dst_x, int dst_y, int src_x, int src_y, int dst_w, int dst_h, int src_w, int src_h )
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.
Returns TRUE on success or FALSE on failure.
dst_image is the destination image,
src_image is the source image identifier. 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.
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
Note: This function requires GD 2.0.1 or later.
Example 1. Simple example
This example will resample an image to half its original size.
<?php // 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;