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imagecopyresampled

(PHP 4 >= 4.0.6, PHP 5)

imagecopyresampled -- Copy and resize part of an image with resampling

Description

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.

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.

Parameters

dst_im

Destination image link resource

src_im

Source image link resource

dst_x

x-coordinate of destination point

dst_y

y-coordinate of destination point

src_x

x-coordinate of source point

src_y

y-coordinate of source point

dst_w

Destination width

dst_h

Destination height

src_w

Source width

src_h

Source height

Return Values

Returns TRUE on success or FALSE on failure.

Examples

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;

// 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.

<?php
// 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:

Notes

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().

See Also

imagecopyresized()

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