PHP Manual: Applies a filter to an image

Description

bool imagefilter(GdImage $image, int $filter, arrayintfloatbool ...$args)

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.';
}

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:

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($logo);
imagedestroy($logo);
?>

The above example will output something similar to:

Output of example : imagefilter() scatter

Notes

Note: The result of IMG_FILTER_SCATTER is always random.

imagefilter