PHP: imagefilter function - 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 , blue , green 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.

arg1

IMG_FILTER_BRIGHTNESS: Brightness level.
IMG_FILTER_CONTRAST: Contrast level.
IMG_FILTER_COLORIZE: Value of red component.
IMG_FILTER_SMOOTH: Smoothness level.

arg2

IMG_FILTER_COLORIZE: Value of green component.

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
5.2.5	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.';
}
?>

Notes

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