Data Structures
struct	gdScatter
	Options to Scatter an image. More...

Enumerations
enum	gdPixelateMode { GD_PIXELATE_UPPERLEFT , GD_PIXELATE_AVERAGE }
	gdImagePixelate options More...

Functions
int	gdImagePixelate (gdImagePtr im, int block_size, const unsigned int mode)
	Pixelates an image.

int	gdImageScatter (gdImagePtr im, int sub, int plus)
	Scatter an image.

int	gdImageScatterColor (gdImagePtr im, int sub, int plus, int colors[], unsigned int num_colors)
	Scatter an image with specified colors.

int	gdImageScatterEx (gdImagePtr im, gdScatterPtr s)
	Scatter an image with extended options.

int	gdImageSmooth (gdImagePtr im, float weight)
	Smooth an image.

int	gdImageMeanRemoval (gdImagePtr im)
	Mean removal of an image.

int	gdImageEmboss (gdImagePtr im)
	Emboss an image.

int	gdImageGaussianBlur (gdImagePtr im)
	Gaussian blur of an image Performs a Gaussian blur of radius 1 on the image. The image is modified in place.

int	gdImageEdgeDetectQuick (gdImagePtr src)
	Edge detection of an image.

int	gdImageSelectiveBlur (gdImagePtr src)
	Selective blur of an image.

int	gdImageConvolution (gdImagePtr src, float filter[3][3], float filter_div, float offset)
	Apply a convolution matrix to an image.

int	gdImageColor (gdImagePtr src, const int red, const int green, const int blue, const int alpha)
	Change channel values of an image.

int	gdImageContrast (gdImagePtr src, double contrast)
	Change the contrast of an image.

int	gdImageBrightness (gdImagePtr src, int brightness)
	Change the brightness of an image.

int	gdImageGrayScale (gdImagePtr src)
	Convert an image to grayscale.

int	gdImageNegate (gdImagePtr src)
	Invert an image.

gdImagePtr	gdImageCopyGaussianBlurred (gdImagePtr src, int radius, double sigma)
	Return a copy of the source image src blurred according to the parameters using the Gaussian Blur algorithm. Return a copy of the source image src blurred according to the parameters using the Gaussian Blur algorithm.

Detailed Description

Enumeration Type Documentation

◆ gdPixelateMode

enum gdPixelateMode

gdImagePixelate options

Negate the imag src, white becomes black, The red, green, and blue intensities of an image are negated. White becomes black, yellow becomes blue, etc.

Enumerator
GD_PIXELATE_UPPERLEFT	Use the upper-left pixel of each block
GD_PIXELATE_AVERAGE	Use the average color of each block

Function Documentation

◆ gdImageBrightness()

int gdImageBrightness	(	gdImagePtr	src,
		int	brightness
	)

Change the brightness of an image.

Parameters

src	The image.
brightness	The value to add to the color channels of all pixels.

Returns: Non-zero on success, zero on failure.

See also: gdImageContrast gdImageColor

◆ gdImageColor()

int gdImageColor	(	gdImagePtr	src,
		const int	red,
		const int	green,
		const int	blue,
		const int	alpha
	)

Change channel values of an image.

Parameters

src	The image.
red	The value to add to the red channel of all pixels.
green	The value to add to the green channel of all pixels.
blue	The value to add to the blue channel of all pixels.
alpha	The value to add to the alpha channel of all pixels.

Returns: Non-zero on success, zero on failure.

See also: gdImageBrightness

◆ gdImageContrast()

int gdImageContrast	(	gdImagePtr	src,
		double	contrast
	)

Change the contrast of an image.

Parameters

src	The image.
contrast	The contrast adjustment value. Negative values increase, postive values decrease the contrast. The larger the absolute value, the stronger the effect.

Returns: Non-zero on success, zero on failure.

See also: gdImageBrightness

◆ gdImageConvolution()

int gdImageConvolution	(	gdImagePtr	src,
		float	filter[3][3],
		float	filter_div,
		float	offset
	)

Apply a convolution matrix to an image.

Depending on the matrix, a wide range of effects can be accomplished, e.g. blurring, sharpening, embossing, and edge detection.

Parameters

src	The image.
filter	The 3x3 convolution matrix.
filter_div	The value to divide the convoluted channel values by.
offset	The value to add to the convoluted channel values.

Returns: Non-zero on success, zero on failure.

See also: gdImageEdgeDetectQuick; gdImageGaussianBlur; gdImageEmboss; gdImageMeanRemoval; gdImageSmooth

◆ gdImageCopyGaussianBlurred()

gdImagePtr gdImageCopyGaussianBlurred	(	gdImagePtr	src,
		int	radius,
		double	sigma
	)

Return a copy of the source image src blurred according to the parameters using the Gaussian Blur algorithm. Return a copy of the source image src blurred according to the parameters using the Gaussian Blur algorithm.

radius is a radius, not a diameter so a radius of 2 (for example) will blur across a region 5 pixels across (2 to the center, 1 for the center itself and another 2 to the other edge).

sigma represents the "fatness of the curve (lower == fatter). If sigma is less than or equal to 0, <gdImageCopyGaussianBlurred> ignores it and instead computes an "optimal" value. Be warned that future versions of this function may compute sigma differently. The resulting image is always truecolor. More Details: A Gaussian Blur is generated by replacing each pixel's color values with the average of the surrounding pixels' colors. This region is a circle whose radius is given by argument radius. Thus, a larger radius will yield a blurrier image. This average is not a simple mean of the values. Instead, values are weighted using the Gaussian function (roughly a bell curve centered around the destination pixel) giving it much more influence on the result than its neighbours. Thus, a fatter curve will give the center pixel more weight and make the image less blurry; lower sigma values will yield flatter curves. Currently, <gdImageCopyGaussianBlurred> computes the default sigma as (2/3)*radius Note, however that we reserve the right to change this if we find a better ratio. If you absolutely need the current sigma value, you should set it yourself. @param src the source image @param radius the blur radius (not diameter–range is 2*radius + 1) @param sigma the sigma value or a value <= 0.0 to use the computed default @return The new image or NULL if an error occurred. The result is always truecolor. Example: @code FILE *in; gdImagePtr result, src; in = fopen("foo.png", "rb"); src = gdImageCreateFromPng(in);

result = gdImageCopyGaussianBlurred(im, src->sx / 10, -1.0);

◆ gdImageEdgeDetectQuick()

int gdImageEdgeDetectQuick ( gdImagePtr src )

Edge detection of an image.

(see edge_detect_quick.jpg)

Parameters

src	The image.

Returns: Non-zero on success, zero on failure.

See also: gdImageMeanRemoval gdImageConvolution

◆ gdImageEmboss()

int gdImageEmboss ( gdImagePtr im )

Emboss an image.

(see emboss.jpg)

Parameters

im	The image.

Returns: Non-zero on success, zero on failure.

See also: gdImageConvolution

◆ gdImageGaussianBlur()

int gdImageGaussianBlur ( gdImagePtr im )

Gaussian blur of an image Performs a Gaussian blur of radius 1 on the image. The image is modified in place.

NOTE: You will almost certain want to use gdImageCopyGaussianBlurred instead, as it allows you to change your kernel size and sigma value. Future versions of this function may fall back to calling it instead of gdImageConvolution, causing subtle changes so be warned.

Parameters

im	The image to blur.

Returns: GD_TRUE (1) on success, GD_FALSE (0) on failure.

See also: @gdImageConvolution for more information on how to use convolution matrices to achieve different effects.

◆ gdImageGrayScale()

int gdImageGrayScale ( gdImagePtr src )

Convert an image to grayscale.

The red, green and blue components of each pixel are replaced by 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.

Parameters

src	The image.

Returns: Non-zero on success, zero on failure.

◆ gdImageMeanRemoval()

int gdImageMeanRemoval ( gdImagePtr im )

Mean removal of an image.

(see mean_removal.jpg)

Parameters

im	The image.

Returns: Non-zero on success, zero on failure.

See also: gdImageEdgeDetectQuick gdImageConvolution

◆ gdImageNegate()

int gdImageNegate ( gdImagePtr src )

Invert an image.

Parameters

src	The image.

Returns: Non-zero on success, zero on failure.

◆ gdImagePixelate()

int gdImagePixelate	(	gdImagePtr	im,
		int	block_size,
		const unsigned int	mode
	)

Pixelates an image.

Pixelates an image by dividing it into blocks of the specified size and replacing each block with a single color. The color can be determined by either the upper-left pixel of the block or the average color of all pixels in the block, depending on the mode specified.

Parameters

im	The image to pixelate.
block_size	The size of the blocks to use for pixelation. Must be greater than 0.
mode	The mode to use for determining the color of each block. gdPixelateMode

Returns: Non-zero on success, zero on failure. Failure: Returns zero if im is NULL or block_size is less than or equal to 0.

◆ gdImageScatter()

int gdImageScatter	(	gdImagePtr	im,
		int	sub,
		int	plus
	)

Scatter an image.

Scatters the pixels of an image by randomly adjusting their color values based on the specified subtraction and addition values.

Parameters

im	The image to scatter.
sub	The subtraction value for scattering. Must be greater than or equal to 0.
plus	The addition value for scattering. Must be greater than or equal to 0

Returns: Non-zero on success, zero on failure. Failure: Returns zero if im is NULL, sub or plus is less than 0.

◆ gdImageScatterColor()

int gdImageScatterColor	(	gdImagePtr	im,
		int	sub,
		int	plus,
		int	colors[],
		unsigned int	num_colors
	)

Scatter an image with specified colors.

Scatters the pixels of an image by randomly adjusting their color values based on the specified subtraction and addition values, using a specified set of colors.

Parameters

im	The image to scatter.
sub	The subtraction value for scattering. Must be greater than or equal to 0.
plus	The addition value for scattering. Must be greater than or equal to 0.
colors	An array of colors to use for scattering. Must not be NULL.
num_colors	The number of colors in the colors array. Must be greater than

Returns: Non-zero on success, zero on failure. Failure: Returns zero if im is NULL, sub or plus is less than 0, colors is NULL, or num_colors is 0.

◆ gdImageScatterEx()

int gdImageScatterEx	(	gdImagePtr	im,
		gdScatterPtr	s
	)

Scatter an image with extended options.

Scatters the pixels of an image using the specified scattering options.

Parameters

im	The image to scatter.
s	A pointer to a gdScatter structure containing the scattering options. Must not be NULL.

Returns

◆ gdImageSelectiveBlur()

int gdImageSelectiveBlur ( gdImagePtr src )

Selective blur of an image.

Parameters

src	The image.

Returns: Non-zero on success, zero on failure.

◆ gdImageSmooth()

int gdImageSmooth	(	gdImagePtr	im,
		float	weight
	)

Smooth an image.

(see smooth.jpg)

Parameters

im	The image.
weight	The strength of the smoothing.

Returns: Non-zero on success, zero on failure.

See also: gdImageConvolution

Smooth an image

(see smooth.jpg)

Parameters

src	The source image.
weight	The strength of the smoothing.

Returns: Non-zero on success, zero on failure. Failure: Returns zero if im is NULL or weight is invalid.

See also: gdImageConvolution gdImageGaussianBlur gdImageEmboss gdImageMeanRemoval

Data Structures

Enumerations

Functions

Detailed Description

Enumeration Type Documentation

◆ gdPixelateMode

Function Documentation

◆ gdImageBrightness()

◆ gdImageColor()

◆ gdImageContrast()

◆ gdImageConvolution()

◆ gdImageCopyGaussianBlurred()

◆ gdImageEdgeDetectQuick()

◆ gdImageEmboss()

◆ gdImageGaussianBlur()

◆ gdImageGrayScale()

◆ gdImageMeanRemoval()

◆ gdImageNegate()

◆ gdImagePixelate()

◆ gdImageScatter()

◆ gdImageScatterColor()

◆ gdImageScatterEx()

◆ gdImageSelectiveBlur()

◆ gdImageSmooth()