Applies a filter to an image

# imagefilter

(PHP 5, PHP 7, PHP 8)

imagefilter — Applies a filter to an image

### Description

imagefilter(GdImage `$image`, int `$filter`, array|int|float|bool `...$args`): bool

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

### Parameters

`image`

  A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().

`filter`

  `filter` can be one of the following:

  - `IMG_FILTER_NEGATE`: Reverses all colors of the image.
  - `IMG_FILTER_GRAYSCALE`: Converts the image into grayscale by changing the red, green and blue components to their weighted sum using the same coefficients as the REC.601 luma (Y') calculation. The alpha components are retained. For palette images the result may differ due to palette limitations.
  - `IMG_FILTER_BRIGHTNESS`: Changes the brightness of the image. Use `args` to set the level of brightness. The range for the brightness is -255 to 255.
  - `IMG_FILTER_CONTRAST`: Changes the contrast of the image. Use `args` to set the level of contrast.
  - `IMG_FILTER_COLORIZE`: Like `IMG_FILTER_GRAYSCALE`, except you can specify the color. Use `args`, `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 `args` to set the level of smoothness.
  - `IMG_FILTER_PIXELATE`: Applies pixelation effect to the image, use `args` to set the block size and `arg2` to set the pixelation effect mode.
  - `IMG_FILTER_SCATTER`: Applies scatter effect to the image, use `args` and `arg2` to define the effect strength and additionally `arg3` to only apply the on select pixel colors.
`args`

  - `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.
  - `IMG_FILTER_SCATTER`: Effect substraction level. This must not be higher or equal to the addition level set with `arg2`.
`arg2`

  - `IMG_FILTER_COLORIZE`: Value of green component.
  - `IMG_FILTER_PIXELATE`: Whether to use advanced pixelation effect or not (defaults to `false`).
  - `IMG_FILTER_SCATTER`: Effect addition level.
`arg3`

  - `IMG_FILTER_COLORIZE`: Value of blue component.
  - `IMG_FILTER_SCATTER`: Optional array indexed color values to apply effect at.
`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.

### Errors/Exceptions

Throws a ValueError if `sub` or `plus` would cause over-/underflow with the `IMG_FILTER_SCATTER` `filter`.

### Changelog

Version | Description
--- | ---
8.4.0 | Now throws a ValueError if `sub` or `plus` would cause over-/underflow with the `IMG_FILTER_SCATTER` `filter`.
8.0.0 | `image` expects a GdImage instance now; previously, a valid `gd` resource was expected.
7.4.0 | Scatter support (`IMG_FILTER_SCATTER`) 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.';
}
?>`

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');
}
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');
}
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);
}
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);
// Output the differences
header('Content-Type: image/png');
imagepng($output);
?>`

The above example will output something similar to:

Example #6 imagefilter() scatter example

`<?php
// Load the image
$logo = imagecreatefrompng('./php.png');
// Apply a very soft scatter effect to the image
imagefilter($logo, IMG_FILTER_SCATTER, 3, 5);
// Output the image with the scatter effect
header('Content-Type: image/png');
imagepng($logo);
?>`

The above example will output something similar to:

### Notes

> Note: The result of `IMG_FILTER_SCATTER` is always random.

### See Also

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

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