## XlibRGB

XlibRGB — Rendering RGB buffers to X drawables.

## Synopsis

    #include <gdk-pixbuf/gdk-pixbuf.h>

    struct              XlibRgbCmap;
    enum                XlibRgbDither;
    void                xlib_rgb_init                       (Display *display,
                                                             Screen *screen);
    void                xlib_rgb_init_with_depth            (Display *display,
                                                             Screen *screen,
                                                             int prefDepth);
    unsigned long       xlib_rgb_xpixel_from_rgb            (guint32 rgb);
    void                xlib_rgb_gc_set_foreground          (GC gc,
                                                             guint32 rgb);
    void                xlib_rgb_gc_set_background          (GC gc,
                                                             guint32 rgb);
    void                xlib_draw_rgb_image                 (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *rgb_buf,
                                                             int rowstride);
    void                xlib_draw_rgb_image_dithalign       (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *rgb_buf,
                                                             int rowstride,
                                                             int xdith,
                                                             int ydith);
    void                xlib_draw_rgb_32_image              (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride);
    void                xlib_draw_gray_image                (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride);
    XlibRgbCmap *       xlib_rgb_cmap_new                   (guint32 *colors,
                                                             int n_colors);
    void                xlib_rgb_cmap_free                  (XlibRgbCmap *cmap);
    void                xlib_draw_indexed_image             (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride,
                                                             XlibRgbCmap *cmap);
    Bool                xlib_rgb_ditherable                 (void);
    void                xlib_rgb_set_verbose                (Bool verbose);
    void                xlib_rgb_set_install                (Bool install);
    void                xlib_rgb_set_min_colors             (int min_colors);
    Colormap            xlib_rgb_get_cmap                   (void);
    Visual *            xlib_rgb_get_visual                 (void);
    XVisualInfo *       xlib_rgb_get_visual_info            (void);
    int                 xlib_rgb_get_depth                  (void);
    Display *           xlib_rgb_get_display                (void);
    Screen *            xlib_rgb_get_screen                 (void);

## Description

The XlibRGB set of functions is a port of the GdkRGB library to use plain Xlib and X drawables. You can use these functions to render RGB buffers into drawables very quickly with high-quality dithering.

## Details

### struct XlibRgbCmap

    struct XlibRgbCmap {
      unsigned int colors[256];
      unsigned char lut[256]; /* for 8-bit modes */
    };

FIXME: Describe this.

unsigned int `colors`[256]; | FIXME.
unsigned char `lut`[256]; | FIXME.

### enum XlibRgbDither

    typedef enum {
      XLIB_RGB_DITHER_NONE,
      XLIB_RGB_DITHER_NORMAL,
      XLIB_RGB_DITHER_MAX
    } XlibRgbDither;

These values are used to specify which dithering method should be used. XLIB_RGB_DITHER_NONE will use no dithering and simply map the colors in an RGB buffer to the closest colors that the display can provide. XLIB_RGB_DITHER_NORMAL will provide dithering only on pseudocolor displays. XLIB_RGB_DITHER_MAX will provide dithering on pseudocolor and 16-bit truecolor or “high color” displays.

`XLIB_RGB_DITHER_NONE` | Specifies no dithering.
`XLIB_RGB_DITHER_NORMAL` | Specifies dithering only on pseudocolor displays.
`XLIB_RGB_DITHER_MAX` | Specifies dithering on high color displays.

### xlib_rgb_init ()

    void                xlib_rgb_init                       (Display *display,
                                                             Screen *screen);

Initializes the XlibRGB machinery with the default depth. If you use this function XlibRGB will automatically pick the best visual available on your display. This function or `xlib_rgb_init_with_depth()` must be called before using any of the other functions in XlibRGB.

`display` : | X Display to use.
`screen` : | Screen to use.

### xlib_rgb_init_with_depth ()

    void                xlib_rgb_init_with_depth            (Display *display,
                                                             Screen *screen,
                                                             int prefDepth);

Initializes the XlibRGB machinery with a particular depth you specify, instead of automatically picking the best depth in the display. This function or `xlib_rgb_init()` must be called before using any of the other functions in XlibRGB.

`display` : | X display to use.
`screen` : | Screen to use.
`prefDepth` : | Visual depth to use for color substitution tables. This must be one of the supported visual depths in the specified `display`.

### xlib_rgb_xpixel_from_rgb ()

    unsigned long       xlib_rgb_xpixel_from_rgb            (guint32 rgb);

Converts an RGB triplet into the closest color that XlibRGB visual can handle.

`rgb` : | 32-bit representation of an RGB value, specified as 0x00RRGGBB.
Returns : | X pixel value that corresponds to the closest color in the XlibRGB visual and colormap.

### xlib_rgb_gc_set_foreground ()

    void                xlib_rgb_gc_set_foreground          (GC gc,
                                                             guint32 rgb);

This is a convenience function to set the foreground of a GC from an RGB triplet. It calls `xlib_rgb_xpixel_from_rgb()` internally and uses the returned pixel value to set the GC's foreground.

`gc` : | A graphic context.
`rgb` : | 32-bit representation of an RGB value, specified as 0x00RRGGBB.

### xlib_rgb_gc_set_background ()

    void                xlib_rgb_gc_set_background          (GC gc,
                                                             guint32 rgb);

This is a convenience function to set the background of a GC from an RGB triplet. It calls `xlib_rgb_xpixel_from_rgb()` internally and uses the returned pixel value to set the GC's background.

`gc` : | A graphic context.
`rgb` : | 32-bit representation of an RGB value, specified as 0x00RRGGBB.

### xlib_draw_rgb_image ()

    void                xlib_draw_rgb_image                 (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *rgb_buf,
                                                             int rowstride);

Renders an RGB buffer to a drawable. Pixels are specified as RGB triplets with 8 bits per channel. An image will thus look like an RGBRGBRGBRGB sequence of 8-bit values. This function does not let you specify dither offsets; applications that need to render partial regions of a buffer to build the final image should use `xlib_draw_rgb_image_dithalign()` instead.

`drawable` : | Destination drawable.
`gc` : | A graphic context.
`x` : | Leftmost coordinate of the destination rectangle.
`y` : | Upper coordinate of the destination rectangle.
`width` : | Width of the destination rectangle, in pixels.
`height` : | Height of the destination rectangle, in pixels.
`dith` : | Dithering method to use.
`rgb_buf` : | Pointer to the pixel in the RGB buffer that corresponds to the upper-left corner of the rectangular region to render.
`rowstride` : | Offset between pixel rows in the RGB buffer, in bytes.

### xlib_draw_rgb_image_dithalign ()

    void                xlib_draw_rgb_image_dithalign       (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *rgb_buf,
                                                             int rowstride,
                                                             int xdith,
                                                             int ydith);

Renders an RGB buffer to a drawable. Pixels are specified as RGB triplets with 8 bits per channel. An image will thus look like an RGBRGBRGBRGB sequence of 8-bit values. This function lets you specify a pair of dither offsets. It should be used when you need to render regions of an RGB buffer separately to form the final image; the dither offsets let you align the dither mask appropriately.

`drawable` : | Destination drawable.
`gc` : | A graphic context.
`x` : | Leftmost coordinate of the destination rectangle.
`y` : | Upper coordinate of the destination rectangle.
`width` : | Width of the destination rectangle, in pixels.
`height` : | Height of the destination rectangle, in pixels.
`dith` : | Dithering method to use.
`rgb_buf` : | Pointer to the pixel in the RGB buffer that corresponds to the upper-left corner of the rectangular region to render.
`rowstride` : | Offset between pixel rows in the RGB buffer, in bytes.
`xdith` : | X offset for the dither mask.
`ydith` : | Y offset for the dither mask.

### xlib_draw_rgb_32_image ()

    void                xlib_draw_rgb_32_image              (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride);

This function is analogous to `xlib_draw_rgb_image()`, but it lets you use 32-bit RGB buffers with pixels specified as 0xRRGGBB00. The least-significant 8 bits are actually discarded. This function can lead to faster results than `xlib_draw_rgb_image()` since the pixels are aligned on 32-bit boundaries.

`drawable` : | Destination drawable.
`gc` : | A graphic context.
`x` : | Leftmost coordinate of the destination rectangle.
`y` : | Upper coordinate of the destination rectangle.
`width` : | Width of the destination rectangle, in pixels.
`height` : | Height of the destination rectangle, in pixels.
`dith` : | Dithering method to use.
`buf` : | Pointer to the pixel in the RGB buffer that corresponds to the upper-left corner of the rectangular region to render.
`rowstride` : | Offset between pixel rows in the RGB buffer, in bytes.

### xlib_draw_gray_image ()

    void                xlib_draw_gray_image                (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride);

Renders a grayscale buffer to a drawable. Pixels are specified as 8-bit intensity values. An image will thus look as a GGGGGG sequence of 8-bit values.

`drawable` : | Destination drawable.
`gc` : | A graphic context.
`x` : | Leftmost coordinate of the destination rectangle.
`y` : | Upper coordinate of the destination rectangle.
`width` : | Width of the destination rectangle, in pixels.
`height` : | Height of thd destination rectangle, in pixels.
`dith` : | Dithering method to use.
`buf` : | Pointer to the pixel in the grayscale buffer that corresponds to the upper-left corner of the rectangular region to render.
`rowstride` : | Offset between pixel rows in the grayscale buffer, in pixels.

### xlib_rgb_cmap_new ()

    XlibRgbCmap *       xlib_rgb_cmap_new                   (guint32 *colors,
                                                             int n_colors);

FIXME

`colors` : | FIXME
`n_colors` : | FIXME
Returns : | FIXME

### xlib_rgb_cmap_free ()

    void                xlib_rgb_cmap_free                  (XlibRgbCmap *cmap);

Frees an XlibRGB colormap.

`cmap` : | An XlibRGB colormap.

### xlib_draw_indexed_image ()

    void                xlib_draw_indexed_image             (Drawable drawable,
                                                             GC gc,
                                                             int x,
                                                             int y,
                                                             int width,
                                                             int height,
                                                             XlibRgbDither dith,
                                                             unsigned char *buf,
                                                             int rowstride,
                                                             XlibRgbCmap *cmap);

FIXME

`drawable` : | FIXME
`gc` : | FIXME
`x` : | FIXME
`y` : | FIXME
`width` : | FIXME
`height` : | FIXME
`dith` : | FIXME
`buf` : | FIXME
`rowstride` : | FIXME
`cmap` : | FIXME

### xlib_rgb_ditherable ()

    Bool                xlib_rgb_ditherable                 (void);

Queries whether XlibRGB supports dithering for its chosen visual.

Returns : | TRUE if dithering can be performed for the visual that XlibRGB is using, FALSE otherwise.

### xlib_rgb_set_verbose ()

    void                xlib_rgb_set_verbose                (Bool verbose);

Enables/disables debug spew.

`verbose` : | True to be verbose

### xlib_rgb_set_install ()

    void                xlib_rgb_set_install                (Bool install);

Sets whether we install an RGB colormap.

`install` : | True to install a colormap

### xlib_rgb_set_min_colors ()

    void                xlib_rgb_set_min_colors             (int min_colors);

Sets the minimum number of colors in the color cube.

`min_colors` : | minimum colors to use

### xlib_rgb_get_cmap ()

    Colormap            xlib_rgb_get_cmap                   (void);

Queries the X colormap that XlibRGB is using.

Returns : | An X colormap.

### xlib_rgb_get_visual ()

    Visual *            xlib_rgb_get_visual                 (void);

Queries the visual that XlibRGB is using.

Returns : | An X visual.

### xlib_rgb_get_visual_info ()

    XVisualInfo *       xlib_rgb_get_visual_info            (void);

Queries the visual info structure for the visual that XlibRGB is using.

Returns : | An XVisualInfo structure.

### xlib_rgb_get_depth ()

    int                 xlib_rgb_get_depth                  (void);

Queries the depth of the visual that XlibRGB is using.

Returns : | Bit depth.

### xlib_rgb_get_display ()

    Display *           xlib_rgb_get_display                (void);

Queries the X display that XlibRGB is using.

Returns : | An X display.

### xlib_rgb_get_screen ()

    Screen *            xlib_rgb_get_screen                 (void);

Queries the screen that XlibRGB is using.

Returns : | An X screen.

## See Also

GdkRGB