The gdk-pixbuf Library
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# XlibRGB

## Name

XlibRGB -- Functions for 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);
    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_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);

This is primarily a debugging function. Sets whether you want XlibRGB to print information about the visual and colormap it chooses. You normally do not need to use this function.

`verbose` : | Whether to print visual/colormap debugging information.

### xlib_rgb_set_install ()

    void        xlib_rgb_set_install            (Bool install);

Sets whether XlibRGB should install its own private colormap instead of trying to allocate color cells from the system colormap. This should be called before initializing XlibRGB.

`install` : | Whether to install a private colormap.

### xlib_rgb_set_min_colors ()

    void        xlib_rgb_set_min_colors         (int min_colors);

Sets the minimum number of free color cells that must be available in the system color map for XlibRGB to use it. If the specified number of colors is not available, XlibRGB will install its own private colormap.

`min_colors` : | Minimum number of colors to look for in the system colormap.

### 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

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