Graphics

# Graphics # Colors ## ALLEGRO_COLOR
    struct ALLEGRO_COLOR
An ALLEGRO_COLOR structure describes a color in a device independant way. Use al_map_rgb et al. and al_unmap_rgb et al. to translate from and to various color representations. ## al_map_rgb
    ALLEGRO_COLOR al_map_rgb(
       unsigned char r, unsigned char g, unsigned char b)
Convert r, g, b (ranging from 0-255) into an ALLEGRO_COLOR, using 255 for alpha. See also: al_map_rgba, al_map_rgba_f, al_map_rgb_f ## al_map_rgb_f
    ALLEGRO_COLOR al_map_rgb_f(float r, float g, float b)
Convert r, g, b, (ranging from 0.0f-1.0f) into an ALLEGRO_COLOR, using 1.0f for alpha. See also: al_map_rgba, al_map_rgb, al_map_rgba_f ## al_map_rgba
    ALLEGRO_COLOR al_map_rgba(
       unsigned char r, unsigned char g, unsigned char b, unsigned char a)
Convert r, g, b, a (ranging from 0-255) into an ALLEGRO_COLOR. See also: al_map_rgb, al_map_rgba_f, al_map_rgb_f ## al_map_rgba_f
    ALLEGRO_COLOR al_map_rgba_f(float r, float g, float b, float a)
Convert r, g, b, a (ranging from 0.0f-1.0f) into an ALLEGRO_COLOR. See also: al_map_rgba, al_map_rgb, al_map_rgb_f ## al_unmap_rgb
    void al_unmap_rgb(ALLEGRO_COLOR color,
       unsigned char *r, unsigned char *g, unsigned char *b)
Retrieves components of an ALLEGRO_COLOR, ignoring alpha Components will range from 0-255. See also: al_unmap_rgba, al_unmap_rgba_f, al_unmap_rgb_f ## al_unmap_rgb_f
    void al_unmap_rgb_f(ALLEGRO_COLOR color, float *r, float *g, float *b)
Retrieves components of an ALLEGRO_COLOR, ignoring alpha. Components will range from 0.0f-1.0f. See also: al_unmap_rgba, al_unmap_rgb, al_unmap_rgba_f ## al_unmap_rgba
    void al_unmap_rgba(ALLEGRO_COLOR color,
       unsigned char *r, unsigned char *g, unsigned char *b, unsigned char *a)
Retrieves components of an ALLEGRO_COLOR. Components will range from 0-255. See also: al_unmap_rgb, al_unmap_rgba_f, al_unmap_rgb_f ## al_unmap_rgba_f
    void al_unmap_rgba_f(ALLEGRO_COLOR color,
       float *r, float *g, float *b, float *a)
Retrieves components of an ALLEGRO_COLOR. Components will range from 0.0f-1.0f. See also: al_unmap_rgba, al_unmap_rgb, al_unmap_rgb_f # Locking and pixel formats ## ALLEGRO_LOCKED_REGION
    typedef struct ALLEGRO_LOCKED_REGION {
Users who wish to manually edit or read from a bitmap are required to lock it first. The ALLEGRO_LOCKED_REGION structure represents the locked region of the bitmap. This call will work with any bitmap, including memory bitmaps.
    typedef struct ALLEGRO_LOCKED_REGION {
            void *data; // the bitmap data
            int format; // the pixel format of the data
            int pitch;  // the size in bytes of a single line
                        // pitch may be greater than pixel_size*bitmap->w
                        // i.e. padded with extra bytes
    }
## ALLEGRO_PIXEL_FORMAT
    enum ALLEGRO_PIXEL_FORMAT {
Pixel formats. Each pixel format specifies the exact size and bit layout of a pixel in memory. Components are specified from high bits to low bits, so for example a fully opaque red pixel in ARGB_8888 format is 0xFFFF0000. Note: The pixel format is independent of endianness. That is, in the above example you can always get the red component with (pixel & 0x00ff0000) >> 16 But you can not rely on this code: *(pixel + 2) It will return the red component on little endian systems, but the green component on big endian systems. Also note that Allegro's naming is different from OpenGL naming here, where a format of GL_RGBA8 merely defines the component order and the exact layout including endianness treatment is specified separately. Usually GL_RGBA8 will correspond to ALLEGRO_PIXEL_ABGR_8888 though on little endian systems, so care must be taken (note the reversal of RGBA <-> ABGR). The only exception to this ALLEGRO_PIXEL_FORMAT_ABGR_8888_LE which will always have the components as 4 bytes corresponding to red, green, blue and alpha, in this order, independent of the endianness.
Format Notes |
--- | ---
ALLEGRO_PIXEL_FORMAT_ANY | Let the driver choose a format. This is the default format at program start.
ALLEGRO_PIXEL_FORMAT_ANY_NO_ALPHA | Let the driver choose a format without alpha.
ALLEGRO_PIXEL_FORMAT_ANY_WITH_ALPHA | Let the driver choose a format with alpha.
ALLEGRO_PIXEL_FORMAT_ANY_15_NO_ALPHA | Let the driver choose a 15 bit format without alpha.
ALLEGRO_PIXEL_FORMAT_ANY_15_WITH_ALPHA | Let the driver choose a 15 bit format with alpha.
ALLEGRO_PIXEL_FORMAT_ANY_16_NO_ALPHA | Let the driver choose a 16 bit format without alpha.
ALLEGRO_PIXEL_FORMAT_ANY_16_WITH_ALPHA | Let the driver choose a 16 bit format with alpha.
ALLEGRO_PIXEL_FORMAT_ANY_24_NO_ALPHA | Let the driver choose a 24 bit format without alpha.
ALLEGRO_PIXEL_FORMAT_ANY_24_WITH_ALPHA | Let the driver choose a 24 bit format with alpha.
ALLEGRO_PIXEL_FORMAT_ANY_32_NO_ALPHA | Let the driver choose a 32 bit format without alpha.
ALLEGRO_PIXEL_FORMAT_ANY_32_WITH_ALPHA | Let the driver choose a 32 bit format with alpha.
ALLEGRO_PIXEL_FORMAT_ARGB_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_RGBA_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_ARGB_4444 | 16 bit
ALLEGRO_PIXEL_FORMAT_RGB_888 | 24 bit
ALLEGRO_PIXEL_FORMAT_RGB_565 | 16 bit
ALLEGRO_PIXEL_FORMAT_RGB_555 | 15 bit
ALLEGRO_PIXEL_FORMAT_RGBA_5551 | 16 bit
ALLEGRO_PIXEL_FORMAT_ARGB_1555 | 16 bit
ALLEGRO_PIXEL_FORMAT_ABGR_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_XBGR_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_BGR_888 | 24 bit
ALLEGRO_PIXEL_FORMAT_BGR_565 | 16 bit
ALLEGRO_PIXEL_FORMAT_BGR_555 | 15 bit
ALLEGRO_PIXEL_FORMAT_RGBX_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_XRGB_8888 | 32 bit
ALLEGRO_PIXEL_FORMAT_ABGR_F32 | 128 bit
ALLEGRO_PIXEL_FORMAT_ABGR_8888_LE | Like the version without _LE, but the component order is guaranteed to be red, green, blue, alpha. This only makes a difference on big endian systems, on little endian it is just an alias.
## al_get_pixel_size
    int al_get_pixel_size(int format)
## al_get_pixel_format_bits
    int al_get_pixel_format_bits(int format)
## al_lock_bitmap
    ALLEGRO_LOCKED_REGION *al_lock_bitmap(ALLEGRO_BITMAP *bitmap, int format, int flags)
Lock an entire bitmap for reading or writing. If the bitmap is a display bitmap it will be updated from system memory after the bitmap is unlocked (unless locked read only). Returns NULL if the bitmap cannot be locked, e.g. the bitmap was locked previously and not unlocked. Flags are: ALLEGRO_LOCK_READONLY - The locked region will not be written to. This can be faster if the bitmap is a video texture, as it can be discarded after the lock instead of uploaded back to the card. ALLEGRO_LOCK_WRITEONLY - The locked region will not be read from. This can be faster if the bitmap is a video texture, as no data need to be read from the video card. You are required to fill in all pixels before unlocking the bitmap again, so be careful when using this flag. 'format' indicates the pixel format that the returned buffer will be in. To lock in the same format as the bitmap stores it's data internally, call with `al_get_bitmap_format(bitmap)` as the format or use ALLEGRO_FORMAT_ANY. Locking in the native format will usually be faster. Note: While a bitmap is locked, you can not use any drawing operations on it (with the sole exception of al_put_pixel and al_draw_pixel). ## al_lock_bitmap_region
    ALLEGRO_LOCKED_REGION *al_lock_bitmap_region(ALLEGRO_BITMAP *bitmap,
        int x, int y,
        int width, int height,
            int format,
        int flags)
Like al_lock_bitmap, but only locks a specific area of the bitmap. If the bitmap is a display bitmap, only that area of the texture will be updated when it is unlocked. Locking only the region you indend to modify will be faster than locking the whole bitmap. See Also: al_lock_bitmap ## al_unlock_bitmap
    void al_unlock_bitmap(ALLEGRO_BITMAP *bitmap)
Unlock a previously locked bitmap or bitmap region. If the bitmap is a display bitmap, the texture will be updated to match the system memory copy (unless it was locked read only). # Bitmap creation ## al_clone_bitmap
    ALLEGRO_BITMAP *al_clone_bitmap(ALLEGRO_BITMAP *bitmap)
Clone a bitmap "exactly", formats can be different. ## al_create_bitmap
    ALLEGRO_BITMAP *al_create_bitmap(int w, int h)
Creates a new bitmap using the bitmap format and flags for the current thread. Blitting between bitmaps of differing formats, or blitting between memory bitmaps and display bitmaps may be slow. Unless you set the ALLEGRO_MEMORY_BITMAP flag, the bitmap is created for the current display. Blitting to another display may be slow. If a display bitmap is created, there may be limitations on the allowed dimensions. For example a DirectX or OpenGL backend usually has a maximum allowed texture size - so if bitmap creation fails for very large dimensions, you may want to re-try with a smaller bitmap. See Also: al_set_new_bitmap_format, al_set_new_bitmap_flags ## al_create_sub_bitmap
    ALLEGRO_BITMAP *al_create_sub_bitmap(ALLEGRO_BITMAP *parent,
       int x, int y, int w, int h)
Creates a sub-bitmap of the parent, at the specified coordinates and of the specified size. A sub-bitmap is a bitmap that shares drawing memory with a pre-existing (parent) bitmap, but possibly with a different size and clipping settings. If the sub-bitmap does not lie completely inside the parent bitmap, then it is automatically clipped so that it does. The parent bitmap's clipping rectangles are ignored. If a sub-bitmap was not or cannot be created then NULL is returned. Note that destroying parents of sub-bitmaps will not destroy the sub-bitmaps; instead the sub-bitmaps become invalid and should no longer be used. ## al_destroy_bitmap
    void al_destroy_bitmap(ALLEGRO_BITMAP *bitmap)
Destroys the given bitmap, freeing all resources used by it. Does nothing if given the null pointer. ## al_get_new_bitmap_flags
    int al_get_new_bitmap_flags(void)
Returns the flags used for newly created bitmaps. ## al_get_new_bitmap_format
    int al_get_new_bitmap_format(void)
Returns the format used for newly created bitmaps. ## al_load_bitmap
    ALLEGRO_BITMAP *al_load_bitmap(char const *filename)
    ALLEGRO_BITMAP *al_load_bitmap(const char *filename)
Load a bitmap from a file using the bitmap format and flags of the current thread. See Also: al_set_new_bitmap_format, al_set_new_bitmap_flags ## al_set_new_bitmap_flags
    void al_set_new_bitmap_flags(int flags)
Sets the flags to use for newly created bitmaps. Valid flags are: ALLEGRO_MEMORY_BITMAP - The bitmap will use a format most closely resembling the format used in the bitmap file and al_create_memory_bitmap will be used to create it. If this flag is not specified, al_create_bitmap will be used instead and the display driver will determine the format. XXX al_create_memory_bitmap doesn't exist any more ALLEGRO_KEEP_BITMAP_FORMAT - Only used when loading bitmaps from disk files, forces the resulting ALLEGRO_BITMAP to use the same format as the file. ALLEGRO_FORCE_LOCKING - When drawing to a bitmap with this flag set, always use pixel locking and draw to it using Allegro's software drawing primitives. This should never be used if you plan to draw to the bitmap using Allegro's graphics primitives as it would cause severe performance penalties. However if you know that the bitmap will only ever be accessed by locking it, no unneeded FBOs will be created for it in the OpenGL drivers. ALLEGRO_NO_PRESERVE_TEXTURE - Normally, every effort is taken to preserve the contents of bitmaps since some drivers may forget them. This can take extra time. If you know it doesn't matter if a bitmap keeps it's image, for example a temporary buffer, use this flag to tell Allegro no to attempt to preserve the contents of bitmaps created after this flag is set. This can lead to speed improvements in your program. ## al_set_new_bitmap_format
    void al_set_new_bitmap_format(int format)
Sets the pixel format for newly created bitmaps. The default format is 0 and means the display driver will choose the best format. # Bitmap properties ## al_get_bitmap_flags
    int al_get_bitmap_flags(ALLEGRO_BITMAP *bitmap)
Return the flags user to create the bitmap. ## al_get_bitmap_format
    int al_get_bitmap_format(ALLEGRO_BITMAP *bitmap)
Returns the pixel format of a bitmap. ## al_get_bitmap_height
    int al_get_bitmap_height(ALLEGRO_BITMAP *bitmap)
Returns the height of a bitmap in pixels. ## al_get_bitmap_width
    int al_get_bitmap_width(ALLEGRO_BITMAP *bitmap)
Returns the width of a bitmap in pixels. ## al_get_pixel
    ALLEGRO_COLOR al_get_pixel(ALLEGRO_BITMAP *bitmap, int x, int y)
Get a pixel's color value from the specified bitmap. ## al_is_bitmap_locked
    bool al_is_bitmap_locked(ALLEGRO_BITMAP *bitmap)
Returns whether or not a bitmap is already locked. ## al_is_compatible_bitmap
    bool al_is_compatible_bitmap(ALLEGRO_BITMAP *bitmap)
D3D and OpenGL allow sharing a texture in a way so it can be used for multiple windows. Each ALLEGRO_BITMAP created with al_create_bitmap however is usually tied to a single ALLEGRO_DISPLAY. This function can be used to know if the bitmap is compatible with the current display, even if it is another display than the one it was created with. It returns true if the bitmap is compatible (things like a cached texture version can be used) and false otherwise (blitting in the current display will be slow). The only time this function is useful is if you are using multiple windows and need accelerated blitting of the same bitmaps to both. ## al_is_sub_bitmap
    bool al_is_sub_bitmap(ALLEGRO_BITMAP *bitmap)
Returns true if the specified bitmap is a sub-bitmap, false otherwise. # Drawing operations All drawing operations draw to the current "target bitmap" of the current thread. Initially, the target bitmap will be the backbuffer of the last display created in a thread. ## al_clear_to_color
    void al_clear_to_color(ALLEGRO_COLOR color)
Clear the complete target bitmap, but confined by the clipping rectangle. ## al_draw_bitmap
    void al_draw_bitmap(ALLEGRO_BITMAP *bitmap, float dx, float dy, int flags)
Draws an unscaled, unrotated bitmap at the given position to the current target bitmap (see al_set_target_bitmap). flags can be a combination of: ALLEGRO_FLIP_HORIZONTAL - flip the bitmap about the y-axis ALLEGRO_FLIP_VERTICAL - flip the bitmap about the x-axis ## al_draw_bitmap_region
    void al_draw_bitmap_region(ALLEGRO_BITMAP *bitmap, float sx, float sy,
        float sw, float sh, float dx, float dy, int flags)
Draws a region of the given bitmap to the target bitmap. sx - source x sy - source y sw - source width (width of region to blit) sh - source height (height of region to blit) dx - destination x dy - destination y flags - same as for al_draw_bitmap ## al_draw_pixel
    void al_draw_pixel(float x, float y, ALLEGRO_COLOR color)
Draws a single pixel at x, y. This function, unlike al_put_pixel, does blending. x - destination x y - destination y color - color of the pixel ## al_draw_rotated_bitmap
    void al_draw_rotated_bitmap(ALLEGRO_BITMAP *bitmap, float cx, float cy,
        float dx, float dy, float angle, int flags)
Draws a rotated version of the given bitmap to the target bitmap. The bitmap is rotated by 'angle' radians counter clockwise. The point at cx/cy inside the bitmap will be drawn at dx/dy and the bitmap is rotated around this point. cx - center x cy - center y dx - destination x dy - destination y angle - angle by which to rotate flags - same as for al_draw_bitmap ## al_draw_rotated_scaled_bitmap
    void al_draw_rotated_scaled_bitmap(ALLEGRO_BITMAP *bitmap, float cx, float cy,
        float dx, float dy, float xscale, float yscale, float angle,
        int flags)
Like al_draw_rotated_bitmap, but can also scale the bitmap. The point at cx/cy in the bitmap will be drawn at dx/dy and the bitmap is rotated and scaled around this point. cx - center x cy - center y dx - destination x dy - destination y xscale - how much to scale on the x-axis (e.g. 2 for twice the size) yscale - how much to scale on the y-axis angle - angle by which to rotate flags - same as for al_draw_bitmap ## al_draw_scaled_bitmap
    void al_draw_scaled_bitmap(ALLEGRO_BITMAP *bitmap, float sx, float sy,
        float sw, float sh, float dx, float dy, float dw, float dh, int flags)
Draws a scaled version of the given bitmap to the target bitmap. sx - source x sy - source y sw - source width sh - source height dx - destination x dy - destination y dw - destination width dh - destination height flags - same as for al_draw_bitmap ## al_get_target_bitmap
    ALLEGRO_BITMAP *al_get_target_bitmap(void)
Return the target bitmap of the current display. ## al_put_pixel
    void al_put_pixel(int x, int y, ALLEGRO_COLOR color)
Draw a single pixel on the target bitmap. ## al_set_target_bitmap
    void al_set_target_bitmap(ALLEGRO_BITMAP *bitmap)
Select the bitmap to which all subsequent drawing operations in the calling thread will draw. # Blending modes ## al_get_blender
    void al_get_blender(int *src, int *dst, ALLEGRO_COLOR *color)
Returns the active blender for the current thread. You can pass NULL for values you are not interested in. ## al_get_separate_blender
    void al_get_separate_blender(int *src, int *dst, int *alpha_src,
       int *alpha_dst, ALLEGRO_COLOR *color)
Returns the active blender for the current thread. You can pass NULL for values you are not interested in. ## al_set_blender
    void al_set_blender(int src, int dst, ALLEGRO_COLOR color)
Sets the function to use for blending for the current thread. Blending means, the source and destination colors are combined in drawing operations. Assume, the source color (e.g. color of a rectangle to draw, or pixel of a bitmap to draw), is given as its red/green/blue/alpha components (if the bitmap has no alpha, it always is assumed to be fully opaque, so 255 for 8-bit or 1.0 for floating point): sr, sg, sb, sa. And this color is drawn to a destination, which already has a color: dr, dg, db, da. Blending formula: The conceptional formula used by Allegro to draw any pixel then is
    r = dr * dst + sr * src
    g = dg * dst + sg * src
    b = db * dst + sb * src
    a = da * dst + sa * src
Blending functions: Valid values for and passed to this function are ALLEGRO_ZERO - src, dst = 0 ALLEGRO_ONE - src, dst = 1 ALLEGRO_ALPHA - src, dst = sa ALLEGRO_INVERSE_ALPHA - src, dst = 1 - sa The color parameter specified the blend color, it is multipled with the source color before the above blending operation. Blending examples: So for example, to restore the default of using alpha blending, you would use (pseudo code)
    al_set_blender(ALLEGRO_ALPHA, ALLEGRO_INVERSE_ALPHA, {1, 1, 1, 1})
If in addition you want to draw half transparently
    al_set_blender(ALLEGRO_ALPHA, ALLEGRO_INVERSE_ALPHA, {1, 1, 1, 0.5})
Additive blending would be achieved with
    al_set_blender(ALLEGRO_ONE, ALLEGRO_ONE, {1, 1, 1, 1})
Copying the source to the destination (including alpha) unmodified
    al_set_blender(ALLEGRO_ONE, ALLEGRO_ZERO, {1, 1, 1, 1})
## al_set_separate_blender
    void al_set_separate_blender(int src, int dst, int alpha_src,
       int alpha_dst, ALLEGRO_COLOR color)
Like al_set_blender, but allows specifying a separate blending operation for the alpha channel. # Clipping ## al_get_clipping_rectangle
    /* XXX this seems like it belongs in bitmap_new.c */
    void al_get_clipping_rectangle(int *x, int *y, int *w, int *h)
Gets the clipping rectangle of the target bitmap. ## al_set_clipping_rectangle
    /* XXX this seems like it belongs in bitmap_new.c */
    void al_set_clipping_rectangle(int x, int y, int width, int height)
Set the region of the target bitmap or display that pixels get clipped to. The default is to clip pixels to the entire bitmap. # Miscellaneous ## al_convert_mask_to_alpha
    void al_convert_mask_to_alpha(ALLEGRO_BITMAP *bitmap, ALLEGRO_COLOR mask_color)
Convert the given mask color to an alpha channel in the bitmap. Can be used to convert older 4.2-style bitmaps with magic pink to alpha-ready bitmaps.

Last updated: 2009-05-04 10:18:42 UTC