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# imagefilter

(PHP 5)

imagefilter — Applies a filter to an image

### Description

bool imagefilter ( resource `$image` , int `$filtertype` [, int `$arg1` [, int `$arg2` [, int `$arg3` [, int `$arg4` ]]]] )

imagefilter() applies the given filter `filtertype` on the `image`.

### Parameters

`image`

  An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().

`filtertype`

  `filtertype` can be one of the following:

  - `IMG_FILTER_NEGATE`: Reverses all colors of the image.
  - `IMG_FILTER_GRAYSCALE`: Converts the image into grayscale.
  - `IMG_FILTER_BRIGHTNESS`: Changes the brightness of the image. Use `arg1` to set the level of brightness.
  - `IMG_FILTER_CONTRAST`: Changes the contrast of the image. Use `arg1` to set the level of contrast.
  - `IMG_FILTER_COLORIZE`: Like `IMG_FILTER_GRAYSCALE`, except you can specify the color. Use `arg1`, `arg2` and `arg3` in the form of `red`, `green`, `blue` and `arg4` for the `alpha` channel. The range for each color is 0 to 255.
  - `IMG_FILTER_EDGEDETECT`: Uses edge detection to highlight the edges in the image.
  - `IMG_FILTER_EMBOSS`: Embosses the image.
  - `IMG_FILTER_GAUSSIAN_BLUR`: Blurs the image using the Gaussian method.
  - `IMG_FILTER_SELECTIVE_BLUR`: Blurs the image.
  - `IMG_FILTER_MEAN_REMOVAL`: Uses mean removal to achieve a "sketchy" effect.
  - `IMG_FILTER_SMOOTH`: Makes the image smoother. Use `arg1` to set the level of smoothness.
  - `IMG_FILTER_PIXELATE`: Applies pixelation effect to the image, use `arg1` to set the block size and `arg2` to set the pixelation effect mode.
`arg1`

  - `IMG_FILTER_BRIGHTNESS`: Brightness level.
  - `IMG_FILTER_CONTRAST`: Contrast level.
  - `IMG_FILTER_COLORIZE`: Value of red component.
  - `IMG_FILTER_SMOOTH`: Smoothness level.
  - `IMG_FILTER_PIXELATE`: Block size in pixels.
`arg2`

  - `IMG_FILTER_COLORIZE`: Value of green component.
  - `IMG_FILTER_PIXELATE`: Whether to use advanced pixelation effect or not (defaults to `FALSE`).
`arg3`

  - `IMG_FILTER_COLORIZE`: Value of blue component.
`arg4`

  - `IMG_FILTER_COLORIZE`: Alpha channel, A value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Changelog

Version | Description
--- | ---
5.3.0 | Pixelation support (`IMG_FILTER_PIXELATE`) was added.
5.2.5 | Alpha support for `IMG_FILTER_COLORIZE` was added.

### Examples

Example #1 imagefilter() grayscale example

`<?php
$im = imagecreatefrompng('dave.png');
if($im && imagefilter($im, IMG_FILTER_GRAYSCALE))
{
echo 'Image converted to grayscale.';
imagepng($im, 'dave.png');
}
else
{
echo 'Conversion to grayscale failed.';
}
imagedestroy($im);
?>`

Example #2 imagefilter() brightness example

`<?php
$im = imagecreatefrompng('sean.png');
if($im && imagefilter($im, IMG_FILTER_BRIGHTNESS, 20))
{
echo 'Image brightness changed.';
imagepng($im, 'sean.png');
imagedestroy($im);
}
else
{
echo 'Image brightness change failed.';
}
?>`

Example #3 imagefilter() colorize example

`<?php
$im = imagecreatefrompng('philip.png');
/* R, G, B, so 0, 255, 0 is green */
if($im && imagefilter($im, IMG_FILTER_COLORIZE, 0, 255, 0))
{
echo 'Image successfully shaded green.';
imagepng($im, 'philip.png');
imagedestroy($im);
}
else
{
echo 'Green shading failed.';
}
?>`

Example #4 imagefilter() negate example

`<?php
// Define our negate function so its portable for
// php versions without imagefilter()
function negate($im)
{
if(function_exists('imagefilter'))
{
return imagefilter($im, IMG_FILTER_NEGATE);
}
for($x = 0; $x < imagesx($im); ++$x)
{
for($y = 0; $y < imagesy($im); ++$y)
{
$index = imagecolorat($im, $x, $y);
$rgb = imagecolorsforindex($index);
$color = imagecolorallocate($im, 255 - $rgb['red'], 255 - $rgb['green'], 255 - $rgb['blue']);
imagesetpixel($im, $x, $y, $color);
}
}
return(true);
}
$im = imagecreatefromjpeg('kalle.jpg');
if($im && negate($im))
{
echo 'Image successfully converted to negative colors.';
imagejpeg($im, 'kalle.jpg', 100);
imagedestroy($im);
}
else
{
echo 'Converting to negative colors failed.';
}
?>`

Example #5 imagefilter() pixelate example

`<?php
// Load the PHP logo, we need to create two instances
// to show the differences
$logo1 = imagecreatefrompng('./php.png');
$logo2 = imagecreatefrompng('./php.png');
// Create the image instance we want to show the
// differences on
$output = imagecreatetruecolor(imagesx($logo1) * 2, imagesy($logo1));
// Apply pixelation to each instance, with a block
// size of 3
imagefilter($logo1, IMG_FILTER_PIXELATE, 3);
imagefilter($logo2, IMG_FILTER_PIXELATE, 3, true);
// Merge the differences onto the output image
imagecopy($output, $logo1, 0, 0, 0, 0, imagesx($logo1) - 1, imagesy($logo1) - 1);
imagecopy($output, $logo2, imagesx($logo2), 0, 0, 0, imagesx($logo2) - 1, imagesy($logo2) - 1);
imagedestroy($logo1);
imagedestroy($logo2);
// Output the differences
header('Content-Type: image/png');
imagepng($output);
imagedestroy($output);
?>`

The above example will output something similar to:

### Notes

> Note: This function is only available if PHP is compiled with the bundled version of the GD library.

### See Also

- imageconvolution() - Apply a 3x3 convolution matrix, using coefficient and offset

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GD and Image Functions
PHP Manual