Data Structures
struct	gdAutoCropOptions
	Options for automatic cropping. More...

struct	gdScaleOptions

Macros
#define	GD_SCALE_INTERPOLATION_AUTO -1
	Let gdImageScaleWithOptions choose the interpolation method from the scale direction.

Enumerations
enum	gdInterpolationMethod { GD_DEFAULT = 0 , GD_BELL , GD_BESSEL , GD_BILINEAR_FIXED , GD_BICUBIC , GD_BICUBIC_FIXED , GD_BLACKMAN , GD_BOX , GD_BSPLINE , GD_CATMULLROM , GD_GAUSSIAN , GD_GENERALIZED_CUBIC , GD_HERMITE , GD_HAMMING , GD_HANNING , GD_MITCHELL , GD_NEAREST_NEIGHBOUR , GD_POWER , GD_QUADRATIC , GD_SINC , GD_TRIANGLE , GD_WEIGHTED4 , GD_LINEAR , GD_LANCZOS3 , GD_LANCZOS8 , GD_BLACKMAN_BESSEL , GD_BLACKMAN_SINC , GD_QUADRATIC_BSPLINE , GD_CUBIC_SPLINE , GD_COSINE , GD_WELSH , GD_METHOD_COUNT = 30 }
	gdInterpolationMethod More...

enum	gdCropMode { GD_CROP_DEFAULT = 0 , GD_CROP_TRANSPARENT , GD_CROP_BLACK , GD_CROP_WHITE , GD_CROP_SIDES , GD_CROP_THRESHOLD }

enum	gdScaleFit { GD_SCALE_FIT_COVER , GD_SCALE_FIT_CONTAIN , GD_SCALE_FIT_FILL , GD_SCALE_FIT_INSIDE , GD_SCALE_FIT_OUTSIDE }

enum	gdScaleGravity { GD_SCALE_GRAVITY_NORTHWEST , GD_SCALE_GRAVITY_NORTH , GD_SCALE_GRAVITY_NORTHEAST , GD_SCALE_GRAVITY_WEST , GD_SCALE_GRAVITY_CENTER , GD_SCALE_GRAVITY_EAST , GD_SCALE_GRAVITY_SOUTHWEST , GD_SCALE_GRAVITY_SOUTH , GD_SCALE_GRAVITY_SOUTHEAST }

enum	gdScaleStrategy { GD_SCALE_STRATEGY_NONE , GD_SCALE_STRATEGY_ENTROPY , GD_SCALE_STRATEGY_ATTENTION }

enum	gdInterestingMethod { GD_INTERESTING_ENTROPY , GD_INTERESTING_ATTENTION }
	Methods used to find an interesting crop region. More...

enum	gdAffineStandardMatrix { GD_AFFINE_TRANSLATE = 0 , GD_AFFINE_SCALE , GD_AFFINE_ROTATE , GD_AFFINE_SHEAR_HORIZONTAL , GD_AFFINE_SHEAR_VERTICAL }
	Standard affine matrix operations. More...

Functions
void	gdImageFlipHorizontal (gdImagePtr im)
	Flip an image vertically.

void	gdImageFlipVertical (gdImagePtr im)
	Flip an image horizontally.

void	gdImageFlipBoth (gdImagePtr im)
	Flip an image vertically and horizontally.

gdImagePtr	gdImageCrop (gdImagePtr src, const gdRect *crop)
	Crop an image to a given rectangle.

gdImagePtr	gdImageCropAuto (gdImagePtr im, const unsigned int mode)
	Crop an image automatically.

gdImagePtr	gdImageCropThreshold (gdImagePtr im, const unsigned int color, const float threshold)
	Crop an image using a given color.

gdImagePtr	gdImageAutoCropWithOptions (gdImagePtr src, const gdAutoCropOptions *options)
	Crop an image automatically with options.

int	gdImageSetInterpolationMethod (gdImagePtr im, gdInterpolationMethod id)
	Set the interpolation method stored on an image.

gdInterpolationMethod	gdImageGetInterpolationMethod (gdImagePtr im)
	Return the interpolation method currently stored on an image.

gdImagePtr	gdImageScale (const gdImagePtr src, const unsigned int new_width, const unsigned int new_height)
	Scale an image to an exact width and height using the source image's current gdInterpolationMethod.

gdImagePtr	gdImageScaleWithOptions (const gdImagePtr src, const unsigned int new_width, const unsigned int new_height, const gdScaleOptions *options)
	Scale an image using aspect-ratio, gravity, crop-strategy and interpolation options.

int	gdImageInterestingCropRegion (const gdImagePtr src, unsigned int target_width, unsigned int target_height, gdInterestingMethod method, gdRectPtr crop)
	Find a source crop region with the requested aspect ratio using an interesting-region method.

int	gdImageEntropyCropRegion (const gdImagePtr src, unsigned int target_width, unsigned int target_height, gdRectPtr crop)
	Find a high-entropy source crop region with the requested aspect ratio.

gdImagePtr	gdImageRotateInterpolated (const gdImagePtr src, const float angle, int bgcolor)
	Rotate an image by an arbitrary angle using the source image's current gdInterpolationMethod.

int	gdAffineApplyToPointF (gdPointFPtr dst, const gdPointFPtr src, const double affine[6])
	Apply an affine matrix to a floating-point point.

int	gdAffineInvert (double dst[6], const double src[6])
	Invert an affine matrix.

int	gdAffineFlip (double dst_affine[6], const double src_affine[6], const int flip_h, const int flip_v)
	Build a horizontal and/or vertical flip from an affine matrix.

int	gdAffineConcat (double dst[6], const double m1[6], const double m2[6])
	Concatenate two affine matrices.

int	gdAffineIdentity (double dst[6])
	Store an identity affine matrix.

int	gdAffineScale (double dst[6], const double scale_x, const double scale_y)
	Store a scale affine matrix.

int	gdAffineRotate (double dst[6], const double angle)
	Store a rotation affine matrix.

int	gdAffineShearHorizontal (double dst[6], const double angle)
	Store a horizontal shear affine matrix.

int	gdAffineShearVertical (double dst[6], const double angle)
	Store a vertical shear affine matrix.

int	gdAffineTranslate (double dst[6], const double offset_x, const double offset_y)
	Store a translation affine matrix.

double	gdAffineExpansion (const double src[6])
	Return the linear expansion factor of an affine matrix.

int	gdAffineRectilinear (const double src[6])
	Test whether an affine matrix preserves axis-aligned rectangles.

int	gdAffineEqual (const double matrix1[6], const double matrix2[6])
	Compare two affine matrices.

int	gdTransformAffineGetImage (gdImagePtr *dst, const gdImagePtr src, gdRectPtr src_area, const double affine[6])
	Apply an affine transform to a source region and create an image containing the complete transformed result.

int	gdTransformAffineCopy (gdImagePtr dst, int dst_x, int dst_y, const gdImagePtr src, gdRectPtr src_region, const double affine[6])
	Apply an affine transform to a source region and copy the transformed pixels into an existing destination image.

int	gdTransformAffineBoundingBox (gdRectPtr src, const double affine[6], gdRectPtr bbox)
	Compute the bounding box of a source rectangle after applying an affine transform.

Detailed Description

Image transformation APIs for interpolation, scaling, rotation and affine mapping.

Affine matrices use a six-element double array:

matrix[0] == xx matrix[1] == yx matrix[2] == xy matrix[3] == yy matrix[4] == x0 matrix[5] == y0

A point (x, y) is transformed as:

x_new = xx * x + xy * y + x0 y_new = yx * x + yy * y + y0

Matrix functions to initialize, transform and combine affine matrices used by transform, scale and rotate APIs.

They can be used with gdTransformAffineCopy and are also used in various transformation functions in GD.

Matrices use a six-element double array:

matrix[0] == xx matrix[1] == yx matrix[2] == xy matrix[3] == yy matrix[4] == x0 matrix[5] == y0

where the transformation of a point (x, y) is:

x_new = xx * x + xy * y + x0 y_new = yx * x + yy * y + y0

Macro Definition Documentation

◆ GD_SCALE_INTERPOLATION_AUTO

#define GD_SCALE_INTERPOLATION_AUTO -1

Let gdImageScaleWithOptions choose the interpolation method from the scale direction.

Automatic selection uses GD_LANCZOS3 for downscales or mixed-axis scales, and GD_CATMULLROM for pure upscales.

Enumeration Type Documentation

◆ gdAffineStandardMatrix

enum gdAffineStandardMatrix

Standard affine matrix operations.

Enumerator
GD_AFFINE_TRANSLATE	Translation matrix.
GD_AFFINE_SCALE	Scale matrix.
GD_AFFINE_ROTATE	Rotation matrix.
GD_AFFINE_SHEAR_HORIZONTAL	Horizontal shear matrix.
GD_AFFINE_SHEAR_VERTICAL	Vertical shear matrix.

◆ gdCropMode

enum gdCropMode

Group: Crop

See also: gdImageCropAuto gdImageCropThreshold gdCrop

Enumerator
GD_CROP_DEFAULT	Same as GD_CROP_TRANSPARENT
GD_CROP_TRANSPARENT	Crop using the transparent color
GD_CROP_BLACK	Crop black borders
GD_CROP_WHITE	Crop white borders
GD_CROP_SIDES	Crop using colors of the 4 corners
GD_CROP_THRESHOLD	Crop using a threshold

◆ gdInterestingMethod

enum gdInterestingMethod

Methods used to find an interesting crop region.

See also: gdImageInterestingCropRegion gdImageScaleWithOptions

Enumerator
GD_INTERESTING_ENTROPY	Prefer regions with higher image entropy.
GD_INTERESTING_ATTENTION	Prefer regions with likely visual attention.

◆ gdInterpolationMethod

enum gdInterpolationMethod

gdInterpolationMethod

Interpolation kernels used by image scaling, rotation and affine transformation functions. Newly-created images use GD_BILINEAR_FIXED by default. Call gdImageSetInterpolationMethod on the source image before using APIs that read the image's current interpolation method.

gdImageScaleWithOptions can either use one of these values explicitly or use GD_SCALE_INTERPOLATION_AUTO to choose a method from the requested scale direction.

Note: GD_WEIGHTED4 is not supported by gdImageScale. For downscales or mixed-axis scales, gdImageScale maps the fixed compatibility methods (GD_DEFAULT, GD_BILINEAR_FIXED, GD_LINEAR, GD_BICUBIC_FIXED and GD_BICUBIC) to GD_TRIANGLE to avoid the blur and aliasing of the old fixed scalers.

See also: gdImageSetInterpolationMethod gdImageScale gdImageScaleWithOptions gdImageRotateInterpolated gdTransformAffineCopy

Enumerator
GD_DEFAULT	Compatibility default. Setting this resolves to GD_LINEAR
GD_BELL	Bell filter.
GD_BESSEL	Bessel filter.
GD_BILINEAR_FIXED	Compatibility bilinear scaler.
GD_BICUBIC	Bicubic interpolation.
GD_BICUBIC_FIXED	Compatibility bicubic scaler.
GD_BLACKMAN	Blackman filter.
GD_BOX	Box filter.
GD_BSPLINE	B-spline filter.
GD_CATMULLROM	Catmull-Rom filter.
GD_GAUSSIAN	Gaussian filter.
GD_GENERALIZED_CUBIC	Generalized cubic filter.
GD_HERMITE	Hermite filter.
GD_HAMMING	Hamming filter.
GD_HANNING	Hanning filter.
GD_MITCHELL	Mitchell filter.
GD_NEAREST_NEIGHBOUR	Nearest-neighbour interpolation.
GD_POWER	Power filter.
GD_QUADRATIC	Quadratic filter.
GD_SINC	Sinc filter.
GD_TRIANGLE	Triangle filter.
GD_WEIGHTED4	Four-pixel weighted interpolation for rotation and affine sampling.
GD_LINEAR	Bilinear interpolation.
GD_LANCZOS3	Lanczos filter with radius 3.
GD_LANCZOS8	Lanczos filter with radius 8.
GD_BLACKMAN_BESSEL	Blackman-windowed Bessel filter.
GD_BLACKMAN_SINC	Blackman-windowed sinc filter.
GD_QUADRATIC_BSPLINE	Quadratic B-spline filter.
GD_CUBIC_SPLINE	Cubic spline filter.
GD_COSINE	Cosine filter.
GD_WELSH	Welsh filter.

◆ gdScaleFit

enum gdScaleFit

Constants: gdScaleFit

Controls how gdImageScaleWithOptions maps the source aspect ratio into the requested output size.

Defaults: When gdImageScaleWithOptions receives NULL options, the fit defaults to GD_SCALE_FIT_COVER.

Enumerator
GD_SCALE_FIT_COVER	Preserve aspect ratio, fill requested size, crop overflow.
GD_SCALE_FIT_CONTAIN	Preserve aspect ratio, fit inside requested size, pad the rest.
GD_SCALE_FIT_FILL	Stretch to requested size without preserving aspect ratio.
GD_SCALE_FIT_INSIDE	Preserve aspect ratio; output is no larger than requested size.
GD_SCALE_FIT_OUTSIDE	Preserve aspect ratio; output is no smaller than requested size.

◆ gdScaleGravity

enum gdScaleGravity

Chooses the anchor used when gdImageScaleWithOptions pads or crops an image. North and south refer to the top and bottom of the output; west and east refer to the left and right.

Defaults: When gdImageScaleWithOptions receives NULL options, gravity defaults to GD_SCALE_GRAVITY_CENTER.

Enumerator
GD_SCALE_GRAVITY_NORTHWEST	Anchor to the top-left corner.
GD_SCALE_GRAVITY_NORTH	Anchor to the top edge.
GD_SCALE_GRAVITY_NORTHEAST	Anchor to the top-right corner.
GD_SCALE_GRAVITY_WEST	Anchor to the left edge.
GD_SCALE_GRAVITY_CENTER	Anchor to the center.
GD_SCALE_GRAVITY_EAST	Anchor to the right edge.
GD_SCALE_GRAVITY_SOUTHWEST	Anchor to the bottom-left corner.
GD_SCALE_GRAVITY_SOUTH	Anchor to the bottom edge.
GD_SCALE_GRAVITY_SOUTHEAST	Anchor to the bottom-right corner.

◆ gdScaleStrategy

enum gdScaleStrategy

Constants: gdScaleStrategy

Optional crop strategy for GD_SCALE_FIT_COVER in gdImageScaleWithOptions.

Notes: Entropy and attention strategies are valid only with GD_SCALE_FIT_COVER. If a strategy cannot find an interesting crop, gdImageScaleWithOptions falls back to the normal gravity-based cover crop.

Defaults: When gdImageScaleWithOptions receives NULL options, strategy defaults to GD_SCALE_STRATEGY_NONE.

Enumerator
GD_SCALE_STRATEGY_NONE	Crop using gravity only.
GD_SCALE_STRATEGY_ENTROPY	Prefer a high-entropy crop region.
GD_SCALE_STRATEGY_ATTENTION	Prefer a likely visual-attention crop region.

Function Documentation

◆ gdAffineApplyToPointF()

int gdAffineApplyToPointF	(	gdPointFPtr	dst,
		const gdPointFPtr	src,
		const double	affine[6]
	)

Apply an affine matrix to a floating-point point.

Parameters

dst	- Receives the transformed point.
src	- Source point.
affine	- Matrix in gd's six-value affine form.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineConcat()

int gdAffineConcat	(	double	dst[6],
		const double	m1[6],
		const double	m2[6]
	)

Concatenate two affine matrices.

The result is equivalent to applying m1 and then m2. The destination may be the same array as either input.

Parameters

dst	- Receives the concatenated matrix.
m1	- First matrix.
m2	- Second matrix.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineEqual()

int gdAffineEqual	(	const double	matrix1[6],
		const double	matrix2[6]
	)

Compare two affine matrices.

Parameters

matrix1	- First matrix.
matrix2	- Second matrix.

Returns: GD_TRUE if the matrices are equal within gd's affine tolerance, otherwise GD_FALSE.

◆ gdAffineExpansion()

double gdAffineExpansion ( const double src[6] )

Return the linear expansion factor of an affine matrix.

This is the square root of the factor by which the matrix changes area.

Parameters

src	- Source matrix.

Returns: The expansion factor.

◆ gdAffineFlip()

int gdAffineFlip	(	double	dst_affine[6],
		const double	src_affine[6],
		const int	flip_h,
		const int	flip_v
	)

Build a horizontal and/or vertical flip from an affine matrix.

Parameters

dst_affine	- Receives the flipped matrix.
src_affine	- Source matrix.
flip_h	- Non-zero to flip horizontally.
flip_v	- Non-zero to flip vertically.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineIdentity()

int gdAffineIdentity ( double dst[6] )

Store an identity affine matrix.

Parameters

dst	- Receives the identity matrix.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineInvert()

int gdAffineInvert	(	double	dst[6],
		const double	src[6]
	)

Invert an affine matrix.

Parameters

dst	- Receives the inverse matrix.
src	- Source matrix.

Returns: GD_TRUE on success, or GD_FALSE if the matrix cannot be inverted.

◆ gdAffineRectilinear()

int gdAffineRectilinear ( const double src[6] )

Test whether an affine matrix preserves axis-aligned rectangles.

Parameters

src	- Source matrix.

Returns: GD_TRUE if the matrix is rectilinear, otherwise GD_FALSE.

◆ gdAffineRotate()

int gdAffineRotate	(	double	dst[6],
		const double	angle
	)

Store a rotation affine matrix.

In gd's image coordinate system, increasing y moves downward; positive angles rotate counterclockwise in that system.

Parameters

dst	- Receives the rotation matrix.
angle	- Rotation angle in degrees.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineScale()

int gdAffineScale	(	double	dst[6],
		const double	scale_x,
		const double	scale_y
	)

Store a scale affine matrix.

Parameters

dst	- Receives the scale matrix.
scale_x	- Horizontal scale factor.
scale_y	- Vertical scale factor.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineShearHorizontal()

int gdAffineShearHorizontal	(	double	dst[6],
		const double	angle
	)

Store a horizontal shear affine matrix.

Parameters

dst	- Receives the shear matrix.
angle	- Shear angle in degrees.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineShearVertical()

int gdAffineShearVertical	(	double	dst[6],
		const double	angle
	)

Store a vertical shear affine matrix.

Parameters

dst	- Receives the shear matrix.
angle	- Shear angle in degrees.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdAffineTranslate()

int gdAffineTranslate	(	double	dst[6],
		const double	offset_x,
		const double	offset_y
	)

Store a translation affine matrix.

Parameters

dst	- Receives the translation matrix.
offset_x	- Horizontal offset.
offset_y	- Vertical offset.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdImageAutoCropWithOptions()

gdImagePtr gdImageAutoCropWithOptions	(	gdImagePtr	src,
		const gdAutoCropOptions *	options
	)

Crop an image automatically with options.

This function detects the cropping area according to the given options.

Parameters

src	The image.
options	The cropping options, gdAutoCropOptions.

Returns: The newly created cropped image, or NULL on failure.

◆ gdImageCrop()

gdImagePtr gdImageCrop	(	gdImagePtr	src,
		const gdRect *	crop
	)

Crop an image to a given rectangle.

Parameters

src	The image.
crop	The cropping rectangle, gdRect.

Returns: The newly created cropped image, or NULL on failure.

See also: gdImageCrop gdImageCropThreshold gdImageAutoCropWithOptions

◆ gdImageCropAuto()

gdImagePtr gdImageCropAuto	(	gdImagePtr	im,
		const unsigned int	mode
	)

Crop an image automatically.

This function detects the cropping area according to the given mode.

Parameters

im	The image.
mode	The cropping mode, gdCropMode.

Returns: The newly created cropped image, or NULL on failure.

See also: gdImageCrop gdImageCropThreshold gdImageAutoCropWithOptions

◆ gdImageCropThreshold()

gdImagePtr gdImageCropThreshold	(	gdImagePtr	im,
		const unsigned int	color,
		const float	threshold
	)

Crop an image using a given color.

The threshold defines the tolerance to be used while comparing the image color and the color to crop. The method used to calculate the color difference is based on the color distance in the RGB(A) cube.

Parameters

im	The image.
color	The crop color.
threshold	The crop threshold.

Returns: The newly created cropped image, or NULL on failure.

See also: gdImageCrop gdImageCropThreshold gdImageAutoCropWithOptions

◆ gdImageEntropyCropRegion()

int gdImageEntropyCropRegion	(	const gdImagePtr	src,
		unsigned int	target_width,
		unsigned int	target_height,
		gdRectPtr	crop
	)

Find a high-entropy source crop region with the requested aspect ratio.

Parameters

src	- The source image.
target_width	- The target width used to compute the crop aspect ratio.
target_height	- The target height used to compute the crop aspect ratio.
crop	- Receives the crop rectangle on success.

Returns: GD_TRUE on success, or GD_FALSE on failure.

See also: gdImageInterestingCropRegion

◆ gdImageFlipBoth()

void gdImageFlipBoth ( gdImagePtr im )

Flip an image vertically and horizontally.

The image is mirrored upside-down and left-right.

Parameters

im	The image.

See also: gdImageFlipVertical, gdImageFlipHorizontal

◆ gdImageFlipHorizontal()

void gdImageFlipHorizontal ( gdImagePtr im )

Flip an image vertically.

The image is mirrored upside-down.

Parameters

im	The image.

See also: gdImageFlipHorizontal, gdImageFlipBoth

◆ gdImageFlipVertical()

void gdImageFlipVertical ( gdImagePtr im )

Flip an image horizontally.

The image is mirrored left-right.

Parameters

im	The image.

See also: gdImageFlipVertical, gdImageFlipBoth

File: Transformations

◆ gdImageGetInterpolationMethod()

gdInterpolationMethod gdImageGetInterpolationMethod ( gdImagePtr im )

Return the interpolation method currently stored on an image.

Parameters: im - The image.

Returns: The current interpolation method.

◆ gdImageInterestingCropRegion()

int gdImageInterestingCropRegion	(	const gdImagePtr	src,
		unsigned int	target_width,
		unsigned int	target_height,
		gdInterestingMethod	method,
		gdRectPtr	crop
	)

Find a source crop region with the requested aspect ratio using an interesting-region method.

Parameters

src	- The source image.
target_width	- The target width used to compute the crop aspect ratio.
target_height	- The target height used to compute the crop aspect ratio.
method	- The interesting-region method.
crop	- Receives the crop rectangle on success.

Returns: GD_TRUE on success, or GD_FALSE on failure.

See also: gdInterestingMethod gdImageEntropyCropRegion gdImageScaleWithOptions

◆ gdImageRotateInterpolated()

gdImagePtr gdImageRotateInterpolated	(	const gdImagePtr	src,
		const float	angle,
		int	bgcolor
	)

Rotate an image by an arbitrary angle using the source image's current gdInterpolationMethod.

The returned image is newly allocated and must be destroyed with gdImageDestroy. Palette sources are converted to truecolor internally for arbitrary-angle rotation. Angles that are multiples of 90 degrees use the optimized rotate paths.

Parameters

src	- The source image.
angle	- Rotation angle in degrees.
bgcolor	- Background color for uncovered pixels. For palette sources, this may be a palette index.

Returns: The rotated image on success, or NULL on failure.

Note: bgcolor must be non-negative. The source interpolation method must be a valid concrete method; GD_DEFAULT is not accepted by this function.

See also: gdImageSetInterpolationMethod gdImageRotate90 gdImageRotate180 gdImageRotate270

◆ gdImageScale()

gdImagePtr gdImageScale	(	const gdImagePtr	src,
		const unsigned int	new_width,
		const unsigned int	new_height
	)

Scale an image to an exact width and height using the source image's current gdInterpolationMethod.

The returned image is newly allocated and must be destroyed with gdImageDestroy. If the requested dimensions match the source dimensions, this function returns a clone of the source image. Width and height must be greater than zero.

Notes: GD_WEIGHTED4 is not supported by this function. For downscales and mixed-axis scales, the fixed compatibility methods are sampled with GD_TRIANGLE for better filtering.

Parameters: src - The source image. new_width - The requested output width. new_height - The requested output height.

Returns: The scaled image on success, or NULL on failure.

◆ gdImageScaleWithOptions()

gdImagePtr gdImageScaleWithOptions	(	const gdImagePtr	src,
		const unsigned int	new_width,
		const unsigned int	new_height,
		const gdScaleOptions *	options
	)

Scale an image using aspect-ratio, gravity, crop-strategy and interpolation options.

This is the higher-level scaling API. It can stretch, contain, cover, pad or return an inside/outside size while preserving the source aspect ratio. The returned image is newly allocated and must be destroyed with gdImageDestroy.

Parameters

src	- The source image.
new_width	- The requested width.
new_height	- The requested height.
options	- Scaling options, or NULL for the default options.

Returns: The scaled image on success, or NULL on failure. Caller owns the returned image and must call gdImageDestroy when done. Returns NULL if src is NULL, either dimension is zero, interpolation is invalid, or an entropy/attention strategy is used with a fit other than GD_SCALE_FIT_COVER.

See also: gdScaleOptions gdImageScale gdImageInterestingCropRegion

◆ gdImageSetInterpolationMethod()

int gdImageSetInterpolationMethod	(	gdImagePtr	im,
		gdInterpolationMethod	id
	)

Set the interpolation method stored on an image.

Scaling, rotation and affine transformation functions use this value when they sample pixels from the image. Newly-created images default to GD_BILINEAR_FIXED. Passing GD_DEFAULT is accepted and stores GD_LINEAR.

Some transform APIs have optimized paths for specific methods. In particular, gdImageScale uses GD_TRIANGLE when downscaling or doing a mixed-axis scale with the fixed compatibility methods.

Parameters: im - The image. id - The interpolation method.

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

◆ gdTransformAffineBoundingBox()

int gdTransformAffineBoundingBox	(	gdRectPtr	src,
		const double	affine[6],
		gdRectPtr	bbox
	)

Compute the bounding box of a source rectangle after applying an affine transform.

Parameters

src	- Source rectangle.
affine	- Matrix in gd's six-value affine form.
bbox	- Receives the transformed bounding box.

Returns: GD_TRUE on success, or GD_FALSE on failure.

◆ gdTransformAffineCopy()

int gdTransformAffineCopy	(	gdImagePtr	dst,
		int	dst_x,
		int	dst_y,
		const gdImagePtr	src,
		gdRectPtr	src_region,
		const double	affine[6]
	)

Apply an affine transform to a source region and copy the transformed pixels into an existing destination image.

The source image's current gdInterpolationMethod controls sampling. Transparent samples are skipped. Destination bounds and alpha-blending settings are honored.

Parameters

dst	- Destination image.
dst_x	- Destination x offset.
dst_y	- Destination y offset.
src	- Source image.
src_region	- Source rectangle to transform.
affine	- Matrix in gd's six-value affine form.

Returns: GD_TRUE on success, or GD_FALSE on failure.

See also: gdTransformAffineGetImage gdTransformAffineBoundingBox gdImageSetInterpolationMethod

◆ gdTransformAffineGetImage()

int gdTransformAffineGetImage	(	gdImagePtr *	dst,
		const gdImagePtr	src,
		gdRectPtr	src_area,
		const double	affine[6]
	)

Apply an affine transform to a source region and create an image containing the complete transformed result.

The new image is truecolor with alpha saving enabled. Areas not covered by the transformed source are transparent. The source image's current gdInterpolationMethod controls sampling. Palette sources may be converted to truecolor internally.

Parameters

dst	- Receives the newly-created destination image.
src	- Source image.
src_area	- Source rectangle, or NULL to transform the full image.
affine	- Matrix in gd's six-value affine form.

Returns: GD_TRUE on success, or GD_FALSE on failure. On failure, *dst is NULL.

See also: gdTransformAffineCopy gdTransformAffineBoundingBox gdImageSetInterpolationMethod

Data Structures

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ GD_SCALE_INTERPOLATION_AUTO

Enumeration Type Documentation

◆ gdAffineStandardMatrix

◆ gdCropMode

◆ gdInterestingMethod

◆ gdInterpolationMethod

◆ gdScaleFit

◆ gdScaleGravity

◆ gdScaleStrategy

Function Documentation

◆ gdAffineApplyToPointF()

◆ gdAffineConcat()

◆ gdAffineEqual()

◆ gdAffineExpansion()

◆ gdAffineFlip()

◆ gdAffineIdentity()

◆ gdAffineInvert()

◆ gdAffineRectilinear()

◆ gdAffineRotate()

◆ gdAffineScale()

◆ gdAffineShearHorizontal()

◆ gdAffineShearVertical()

◆ gdAffineTranslate()

◆ gdImageAutoCropWithOptions()

◆ gdImageCrop()

◆ gdImageCropAuto()

◆ gdImageCropThreshold()

◆ gdImageEntropyCropRegion()

◆ gdImageFlipBoth()

◆ gdImageFlipHorizontal()

◆ gdImageFlipVertical()

◆ gdImageGetInterpolationMethod()

◆ gdImageInterestingCropRegion()

◆ gdImageRotateInterpolated()

◆ gdImageScale()

◆ gdImageScaleWithOptions()

◆ gdImageSetInterpolationMethod()

◆ gdTransformAffineBoundingBox()

◆ gdTransformAffineCopy()

◆ gdTransformAffineGetImage()