SDL2_rotozoom.cpp file

Classes

struct tColorRGBA: A 32 bit RGBA pixel.
struct tColorY: A 8bit Y/palette pixel.

Typedefs

using tColorRGBA = struct tColorRGBA: A 32 bit RGBA pixel.
using tColorY = struct tColorY: A 8bit Y/palette pixel.

Functions

auto _colorkey(SDL_Surface* src) -> Uint32: Returns colorkey info for a surface.
auto _shrinkSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int factorx, int factory) -> int: Internal 32 bit integer-factor averaging Shrinker.
auto _shrinkSurfaceY(SDL_Surface* src, SDL_Surface* dst, int factorx, int factory) -> int: Internal 8 bit integer-factor averaging shrinker.
auto _zoomSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int flipx, int flipy, int smooth) -> int: Internal 32 bit Zoomer with optional anti-aliasing by bilinear interpolation.
auto _zoomSurfaceY(SDL_Surface* src, SDL_Surface* dst, int flipx, int flipy) -> int: Internal 8 bit Zoomer without smoothing.
void _transformSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int cx, int cy, int isin, int icos, int flipx, int flipy, int smooth): Internal 32 bit rotozoomer with optional anti-aliasing.
void transformSurfaceY(SDL_Surface* src, SDL_Surface* dst, int cx, int cy, int isin, int icos, int flipx, int flipy): Rotates and zooms 8 bit palette/Y 'src' surface to 'dst' surface without smoothing.
auto rotateSurface90Degrees(SDL_Surface* src, int numClockwiseTurns) -> SDL_Surface*: Rotates a 8/16/24/32 bit surface in increments of 90 degrees.
void _rotozoomSurfaceSizeTrig(int width, int height, double angle, double zoomx, double zoomy, int* dstwidth, int* dstheight, double* canglezoom, double* sanglezoom): Internal target surface sizing function for rotozooms with trig result return.
void rotozoomSurfaceSizeXY(int width, int height, double angle, double zoomx, double zoomy, int* dstwidth, int* dstheight): Returns the size of the resulting target surface for a rotozoomSurfaceXY() call.
void rotozoomSurfaceSize(int width, int height, double angle, double zoom, int* dstwidth, int* dstheight): Returns the size of the resulting target surface for a rotozoomSurface() call.
auto rotozoomSurface(SDL_Surface* src, double angle, double zoom, int smooth) -> SDL_Surface*: Rotates and zooms a surface and optional anti-aliasing.
auto rotozoomSurfaceXY(SDL_Surface* src, double angle, double zoomx, double zoomy, int smooth) -> SDL_Surface*: Rotates and zooms a surface with different horizontal and vertival scaling factors and optional anti-aliasing.
void zoomSurfaceSize(int width, int height, double zoomx, double zoomy, int* dstwidth, int* dstheight): Calculates the size of the target surface for a zoomSurface() call.
auto zoomSurface(SDL_Surface* src, double zoomx, double zoomy, int smooth) -> SDL_Surface*: Zoom a surface by independent horizontal and vertical factors with optional smoothing.
auto shrinkSurface(SDL_Surface* src, int factorx, int factory) -> SDL_Surface*: Shrink a surface by an integer ratio using averaging.

Defines

#define MAX(a, b): Returns maximum of two numbers a and b.
#define GUARD_ROWS: Number of guard rows added to destination surfaces.
#define VALUE_LIMIT: Lower limit of absolute zoom factor or rotation degrees.

Function documentation

int _shrinkSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int factorx, int factory)

Internal 32 bit integer-factor averaging Shrinker.

Parameters
src	The surface to shrink (input).
dst	The shrunken surface (output).
factorx	The horizontal shrinking ratio.
factory	The vertical shrinking ratio.
Returns	0 for success or -1 for error.

Shrinks 32 bit RGBA/ABGR 'src' surface to 'dst' surface. Averages color and alpha values values of src pixels to calculate dst pixels. Assumes src and dst surfaces are of 32 bit depth. Assumes dst surface was allocated with the correct dimensions.

int _shrinkSurfaceY(SDL_Surface* src, SDL_Surface* dst, int factorx, int factory)

Internal 8 bit integer-factor averaging shrinker.

Parameters
src	The surface to shrink (input).
dst	The shrunken surface (output).
factorx	The horizontal shrinking ratio.
factory	The vertical shrinking ratio.
Returns	0 for success or -1 for error.

Shrinks 8bit Y 'src' surface to 'dst' surface. Averages color (brightness) values values of src pixels to calculate dst pixels. Assumes src and dst surfaces are of 8 bit depth. Assumes dst surface was allocated with the correct dimensions.

int _zoomSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int flipx, int flipy, int smooth)

Internal 32 bit Zoomer with optional anti-aliasing by bilinear interpolation.

Parameters
src	The surface to zoom (input).
dst	The zoomed surface (output).
flipx	Flag indicating if the image should be horizontally flipped.
flipy	Flag indicating if the image should be vertically flipped.
smooth	Antialiasing flag; set to SMOOTHING_ON to enable.
Returns	0 for success or -1 for error.

Zooms 32 bit RGBA/ABGR 'src' surface to 'dst' surface. Assumes src and dst surfaces are of 32 bit depth. Assumes dst surface was allocated with the correct dimensions.

int _zoomSurfaceY(SDL_Surface* src, SDL_Surface* dst, int flipx, int flipy)

Internal 8 bit Zoomer without smoothing.

Parameters
src	The surface to zoom (input).
dst	The zoomed surface (output).
flipx	Flag indicating if the image should be horizontally flipped.
flipy	Flag indicating if the image should be vertically flipped.
Returns	0 for success or -1 for error.

Zooms 8bit palette/Y 'src' surface to 'dst' surface. Assumes src and dst surfaces are of 8 bit depth. Assumes dst surface was allocated with the correct dimensions.

void _transformSurfaceRGBA(SDL_Surface* src, SDL_Surface* dst, int cx, int cy, int isin, int icos, int flipx, int flipy, int smooth)

Internal 32 bit rotozoomer with optional anti-aliasing.

Parameters
src	Source surface.
dst	Destination surface.
cx	Horizontal center coordinate.
cy	Vertical center coordinate.
isin	Integer version of sine of angle.
icos	Integer version of cosine of angle.
flipx	Flag indicating horizontal mirroring should be applied.
flipy	Flag indicating vertical mirroring should be applied.
smooth	Flag indicating anti-aliasing should be used.

Rotates and zooms 32 bit RGBA/ABGR 'src' surface to 'dst' surface based on the control parameters by scanning the destination surface and applying optionally anti-aliasing by bilinear interpolation. Assumes src and dst surfaces are of 32 bit depth. Assumes dst surface was allocated with the correct dimensions.

void transformSurfaceY(SDL_Surface* src, SDL_Surface* dst, int cx, int cy, int isin, int icos, int flipx, int flipy)

Rotates and zooms 8 bit palette/Y 'src' surface to 'dst' surface without smoothing.

Parameters
src	Source surface.
dst	Destination surface.
cx	Horizontal center coordinate.
cy	Vertical center coordinate.
isin	Integer version of sine of angle.
icos	Integer version of cosine of angle.
flipx	Flag indicating horizontal mirroring should be applied.
flipy	Flag indicating vertical mirroring should be applied.

Rotates and zooms 8 bit RGBA/ABGR 'src' surface to 'dst' surface based on the control parameters by scanning the destination surface. Assumes src and dst surfaces are of 8 bit depth. Assumes dst surface was allocated with the correct dimensions.

SDL_Surface* rotateSurface90Degrees(SDL_Surface* src, int numClockwiseTurns)

Rotates a 8/16/24/32 bit surface in increments of 90 degrees.

Parameters
src	Source surface to rotate.
numClockwiseTurns	Number of clockwise 90 degree turns to apply to the source.
Returns	The new, rotated surface; or NULL for surfaces with incorrect input format.

Specialized 90 degree rotator which rotates a 'src' surface in 90 degree increments clockwise returning a new surface. Faster than rotozoomer since no scanning or interpolation takes place. Input surface must be 8/16/24/32 bit. (code contributed by J. Schiller, improved by C. Allport and A. Schiffler)

void _rotozoomSurfaceSizeTrig(int width, int height, double angle, double zoomx, double zoomy, int* dstwidth, int* dstheight, double* canglezoom, double* sanglezoom)

Internal target surface sizing function for rotozooms with trig result return.

Parameters
width	The source surface width.
height	The source surface height.
angle	The angle to rotate in degrees.
zoomx	The horizontal scaling factor.
zoomy	The vertical scaling factor.
dstwidth	The calculated width of the destination surface.
dstheight	The calculated height of the destination surface.
canglezoom	The sine of the angle adjusted by the zoom factor.
sanglezoom	The cosine of the angle adjusted by the zoom factor.

void rotozoomSurfaceSizeXY(int width, int height, double angle, double zoomx, double zoomy, int* dstwidth, int* dstheight)

Returns the size of the resulting target surface for a rotozoomSurfaceXY() call.

Parameters
width	The source surface width.
height	The source surface height.
angle	The angle to rotate in degrees.
zoomx	The horizontal scaling factor.
zoomy	The vertical scaling factor.
dstwidth	The calculated width of the rotozoomed destination surface.
dstheight	The calculated height of the rotozoomed destination surface.

void rotozoomSurfaceSize(int width, int height, double angle, double zoom, int* dstwidth, int* dstheight)

Returns the size of the resulting target surface for a rotozoomSurface() call.

Parameters
width	The source surface width.
height	The source surface height.
angle	The angle to rotate in degrees.
zoom	The scaling factor.
dstwidth	The calculated width of the rotozoomed destination surface.
dstheight	The calculated height of the rotozoomed destination surface.

SDL_Surface* rotozoomSurface(SDL_Surface* src, double angle, double zoom, int smooth)

Rotates and zooms a surface and optional anti-aliasing.

Parameters
src	The surface to rotozoom.
angle	The angle to rotate in degrees.
zoom	The scaling factor.
smooth	Antialiasing flag; set to SMOOTHING_ON to enable.
Returns	The new rotozoomed surface.

Rotates and zoomes a 32bit or 8bit 'src' surface to newly created 'dst' surface. 'angle' is the rotation in degrees and 'zoom' a scaling factor. If 'smooth' is set then the destination 32bit surface is anti-aliased. If the surface is not 8bit or 32bit RGBA/ABGR it will be converted into a 32bit RGBA format on the fly.

SDL_Surface* rotozoomSurfaceXY(SDL_Surface* src, double angle, double zoomx, double zoomy, int smooth)

Rotates and zooms a surface with different horizontal and vertival scaling factors and optional anti-aliasing.

Parameters
src	The surface to rotozoom.
angle	The angle to rotate in degrees.
zoomx	The horizontal scaling factor.
zoomy	The vertical scaling factor.
smooth	Antialiasing flag; set to SMOOTHING_ON to enable.
Returns	The new rotozoomed surface.

Rotates and zooms a 32bit or 8bit 'src' surface to newly created 'dst' surface. 'angle' is the rotation in degrees, 'zoomx and 'zoomy' scaling factors. If 'smooth' is set then the destination 32bit surface is anti-aliased. If the surface is not 8bit or 32bit RGBA/ABGR it will be converted into a 32bit RGBA format on the fly.

void zoomSurfaceSize(int width, int height, double zoomx, double zoomy, int* dstwidth, int* dstheight)

Calculates the size of the target surface for a zoomSurface() call.

Parameters
width	The width of the source surface to zoom.
height	The height of the source surface to zoom.
zoomx	The horizontal zoom factor.
zoomy	The vertical zoom factor.
dstwidth	Pointer to an integer to store the calculated width of the zoomed target surface.
dstheight	Pointer to an integer to store the calculated height of the zoomed target surface.

The minimum size of the target surface is 1. The input factors can be positive or negative.

SDL_Surface* zoomSurface(SDL_Surface* src, double zoomx, double zoomy, int smooth)

Zoom a surface by independent horizontal and vertical factors with optional smoothing.

Parameters
src	The surface to zoom.
zoomx	The horizontal zoom factor.
zoomy	The vertical zoom factor.
smooth	Antialiasing flag; set to SMOOTHING_ON to enable.
Returns	The new, zoomed surface.

Zooms a 32bit or 8bit 'src' surface to newly created 'dst' surface. 'zoomx' and 'zoomy' are scaling factors for width and height. If 'smooth' is on then the destination 32bit surface is anti-aliased. If the surface is not 8bit or 32bit RGBA/ABGR it will be converted into a 32bit RGBA format on the fly. If zoom factors are negative, the image is flipped on the axes.

SDL_Surface* shrinkSurface(SDL_Surface* src, int factorx, int factory)

Shrink a surface by an integer ratio using averaging.

Parameters
src	The surface to shrink.
factorx	The horizontal shrinking ratio.
factory	The vertical shrinking ratio.
Returns	The new, shrunken surface.

Shrinks a 32bit or 8bit 'src' surface to a newly created 'dst' surface. 'factorx' and 'factory' are the shrinking ratios (i.e. 2=1/2 the size, 3=1/3 the size, etc.) The destination surface is antialiased by averaging the source box RGBA or Y information. If the surface is not 8bit or 32bit RGBA/ABGR it will be converted into a 32bit RGBA format on the fly. The input surface is not modified. The output surface is newly allocated.

Define documentation

#define GUARD_ROWS

Number of guard rows added to destination surfaces.

This is a simple but effective workaround for observed issues. These rows allocate extra memory and are then hidden from the surface. Rows are added to the end of destination surfaces when they are allocated. This catches any potential overflows which seem to happen with just the right src image dimensions and scale/rotation and can lead to a situation where the program can segfault.