imagefilter() applies the filter filtertype to the image, using args where necessary.
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 args to set the level of brightness.
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 3 separate args, in the form of red, blue, green. 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.
Bemærk: Denne funktion er kun tilgængelig hvis PHP er kompileret med den medfølgende version af GD biblioteket.
Returnerer TRUE ved succes, FALSE ved fejl.