#include <stdlib.h>
#include <string.h>
#include "SDL3_rotozoom.h"

Data Structures
struct	tColorRGBA
	A 32 bit RGBA pixel. More...

struct	tColorY
	A 8bit Y/palette pixel. More...

Macros
#define	MAX(a, b) (((a) > (b)) ? (a) : (b))
	Returns maximum of two numbers a and b.

#define	GUARD_ROWS (2)
	Number of guard rows added to destination surfaces.

#define	VALUE_LIMIT 0.001
	Lower limit of absolute zoom factor or rotation degrees.

Typedefs
typedef struct tColorRGBA	tColorRGBA
	A 32 bit RGBA pixel.

typedef struct tColorY	tColorY
	A 8bit Y/palette pixel.

Functions
static int	_shrinkSurfaceRGBA (SDL_Surface src, SDL_Surface dst, int factorx, int factory)
	Internal 32 bit integer-factor averaging Shrinker.

static 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.

static 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.

SDL_Surface *	rotateSurface90Degrees (SDL_Surface *src, int numClockwiseTurns)
	Rotates a 8/16/24/32 bit surface in increments of 90 degrees.

static 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.

SDL_Surface *	rotozoomSurface (SDL_Surface *src, double angle, double zoom, int smooth)
	Rotates and zooms a surface and optional anti-aliasing.

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.

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.

SDL_Surface *	zoomSurface (SDL_Surface *src, double zoomx, double zoomy, int smooth)
	Zoom a surface by independent horizontal and vertical factors with optional smoothing.

SDL_Surface *	shrinkSurface (SDL_Surface *src, int factorx, int factory)
	Shrink a surface by an integer ratio using averaging.

Macro Definition Documentation

◆ GUARD_ROWS

#define GUARD_ROWS (2)

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.

Definition at line 79 of file SDL3_rotozoom.c.

◆ MAX

#define MAX	(	a,
		b
	)	(((a) > (b)) ? (a) : (b))

Returns maximum of two numbers a and b.

Definition at line 67 of file SDL3_rotozoom.c.

◆ VALUE_LIMIT

#define VALUE_LIMIT 0.001

Lower limit of absolute zoom factor or rotation degrees.

Definition at line 84 of file SDL3_rotozoom.c.

Typedef Documentation

◆ tColorRGBA

typedef struct tColorRGBA tColorRGBA

A 32 bit RGBA pixel.

◆ tColorY

typedef struct tColorY tColorY

A 8bit Y/palette pixel.

Function Documentation

◆ _rotozoomSurfaceSizeTrig()

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

static

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.

Definition at line 688 of file SDL3_rotozoom.c.

Referenced by rotozoomSurfaceSize(), rotozoomSurfaceSizeXY(), and rotozoomSurfaceXY().

◆ _shrinkSurfaceRGBA()

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

static

Internal 32 bit integer-factor averaging Shrinker.

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.

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.

Definition at line 102 of file SDL3_rotozoom.c.

Referenced by shrinkSurface().

◆ _transformSurfaceRGBA()

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

static

Internal 32 bit rotozoomer with optional anti-aliasing.

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.

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.

Definition at line 427 of file SDL3_rotozoom.c.

Referenced by rotozoomSurfaceXY().

◆ _zoomSurfaceRGBA()

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

static

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

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.

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.

Definition at line 190 of file SDL3_rotozoom.c.

Referenced by rotozoomSurfaceXY(), and zoomSurface().

◆ rotateSurface90Degrees()

SDL_Surface * rotateSurface90Degrees	(	SDL_Surface *	src,
		int	numClockwiseTurns
	)

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

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)

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.

Definition at line 539 of file SDL3_rotozoom.c.

◆ rotozoomSurface()

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

Rotates and zooms a surface and optional anti-aliasing.

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.

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.

Definition at line 769 of file SDL3_rotozoom.c.

◆ rotozoomSurfaceSize()

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.

Definition at line 747 of file SDL3_rotozoom.c.

◆ rotozoomSurfaceSizeXY()

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.

Definition at line 730 of file SDL3_rotozoom.c.

◆ rotozoomSurfaceXY()

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.

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.

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.

Definition at line 790 of file SDL3_rotozoom.c.

Referenced by rotozoomSurface().

◆ shrinkSurface()

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

Shrink a surface by an integer ratio using averaging.

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.

Parameters

src	The surface to shrink.
factorx	The horizontal shrinking ratio.
factory	The vertical shrinking ratio.

Returns: The new, shrunken surface.

Definition at line 1175 of file SDL3_rotozoom.c.

◆ zoomSurface()

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

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

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.

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.

Definition at line 1047 of file SDL3_rotozoom.c.

Referenced by change_nation_label(), create_select_tech_icon(), economy_report_dialog_popup(), get_scaled_city_map(), popup_players_dialog(), popup_races_dialog(), popup_worklist_editor(), real_science_report_dialog_update(), redraw_city_dialog(), redraw_happiness_city_dialog(), redraw_unit_info_label(), resize_surface(), resize_surface_box(), and update_intel_dialog().

◆ zoomSurfaceSize()

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.

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

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.

Definition at line 997 of file SDL3_rotozoom.c.

Referenced by rotozoomSurfaceXY(), and zoomSurface().

Data Structures

Macros

Typedefs

Functions

Macro Definition Documentation

◆ GUARD_ROWS

◆ MAX

◆ VALUE_LIMIT

Typedef Documentation

◆ tColorRGBA

◆ tColorY

Function Documentation

◆ _rotozoomSurfaceSizeTrig()

◆ _shrinkSurfaceRGBA()

◆ _transformSurfaceRGBA()

◆ _zoomSurfaceRGBA()

◆ rotateSurface90Degrees()

◆ rotozoomSurface()

◆ rotozoomSurfaceSize()

◆ rotozoomSurfaceSizeXY()

◆ rotozoomSurfaceXY()

◆ shrinkSurface()

◆ zoomSurface()

◆ zoomSurfaceSize()