Pixbufs: GDK 2 Reference Manual

## Pixbufs Pixbufs — Functions for rendering pixbufs on drawables |

## Functions

void | gdk_pixbuf_render_threshold_alpha ()
void | gdk_pixbuf_render_to_drawable ()
void | gdk_pixbuf_render_to_drawable_alpha ()
void | gdk_pixbuf_render_pixmap_and_mask ()
void | gdk_pixbuf_render_pixmap_and_mask_for_colormap ()
GdkPixbuf * | gdk_pixbuf_get_from_drawable ()
GdkPixbuf * | gdk_pixbuf_get_from_image ()

## Includes

    #include <gdk/gdk.h>

## Description

These functions allow to render pixbufs on drawables. Pixbufs are client-side images. For details on how to create and manipulate pixbufs, see the GdkPixbuf API documentation.

## Functions

### gdk_pixbuf_render_threshold_alpha ()

    void
    gdk_pixbuf_render_threshold_alpha (GdkPixbuf *pixbuf,
                                       GdkBitmap *bitmap,
                                       int src_x,
                                       int src_y,
                                       int dest_x,
                                       int dest_y,
                                       int width,
                                       int height,
                                       int alpha_threshold);

Takes the opacity values in a rectangular portion of a pixbuf and thresholds them to produce a bi-level alpha mask that can be used as a clipping mask for a drawable.

#### Parameters

pixbuf | A pixbuf. |
bitmap | Bitmap where the bilevel mask will be painted to. |
src_x | Source X coordinate. |
src_y | source Y coordinate. |
dest_x | Destination X coordinate. |
dest_y | Destination Y coordinate. |
width | Width of region to threshold, or -1 to use pixbuf width |
height | Height of region to threshold, or -1 to use pixbuf height |
alpha_threshold | Opacity values below this will be painted as zero; all other values will be painted as one. |

### gdk_pixbuf_render_to_drawable ()

    void
    gdk_pixbuf_render_to_drawable (GdkPixbuf *pixbuf,
                                   GdkDrawable *drawable,
                                   GdkGC *gc,
                                   int src_x,
                                   int src_y,
                                   int dest_x,
                                   int dest_y,
                                   int width,
                                   int height,
                                   GdkRgbDither dither,
                                   int x_dither,
                                   int y_dither);

`gdk_pixbuf_render_to_drawable` has been deprecated since version 2.4 and should not be used in newly-written code.

This function is obsolete. Use `gdk_draw_pixbuf()` instead.

Renders a rectangular portion of a pixbuf to a drawable while using the specified GC. This is done using GdkRGB, so the specified drawable must have the GdkRGB visual and colormap. Note that this function will ignore the opacity information for images with an alpha channel; the GC must already have the clipping mask set if you want transparent regions to show through.

For an explanation of dither offsets, see the GdkRGB documentation. In brief, the dither offset is important when re-rendering partial regions of an image to a rendered version of the full image, or for when the offsets to a base position change, as in scrolling. The dither matrix has to be shifted for consistent visual results. If you do not have any of these cases, the dither offsets can be both zero.

#### Parameters

pixbuf | A pixbuf. |
drawable | Destination drawable. |
gc | GC used for rendering. |
src_x | Source X coordinate within pixbuf. |
src_y | Source Y coordinate within pixbuf. |
dest_x | Destination X coordinate within drawable. |
dest_y | Destination Y coordinate within drawable. |
width | Width of region to render, in pixels, or -1 to use pixbuf width |
height | Height of region to render, in pixels, or -1 to use pixbuf height |
dither | Dithering mode for GdkRGB. |
x_dither | X offset for dither. |
y_dither | Y offset for dither. |

### gdk_pixbuf_render_to_drawable_alpha ()

    void
    gdk_pixbuf_render_to_drawable_alpha (GdkPixbuf *pixbuf,
                                         GdkDrawable *drawable,
                                         int src_x,
                                         int src_y,
                                         int dest_x,
                                         int dest_y,
                                         int width,
                                         int height,
                                         GdkPixbufAlphaMode alpha_mode,
                                         int alpha_threshold,
                                         GdkRgbDither dither,
                                         int x_dither,
                                         int y_dither);

`gdk_pixbuf_render_to_drawable_alpha` has been deprecated since version 2.4 and should not be used in newly-written code.

This function is obsolete. Use `gdk_draw_pixbuf()` instead.

Renders a rectangular portion of a pixbuf to a drawable. The destination drawable must have a colormap. All windows have a colormap, however, pixmaps only have colormap by default if they were created with a non-`NULL` window argument. Otherwise a colormap must be set on them with gdk_drawable_set_colormap.

On older X servers, rendering pixbufs with an alpha channel involves round trips to the X server, and may be somewhat slow.

#### Parameters

pixbuf | A pixbuf. |
drawable | Destination drawable. |
src_x | Source X coordinate within pixbuf. |
src_y | Source Y coordinates within pixbuf. |
dest_x | Destination X coordinate within drawable. |
dest_y | Destination Y coordinate within drawable. |
width | Width of region to render, in pixels, or -1 to use pixbuf width. |
height | Height of region to render, in pixels, or -1 to use pixbuf height. |
alpha_mode | Ignored. Present for backwards compatibility. |
alpha_threshold | Ignored. Present for backwards compatibility |
dither | Dithering mode for GdkRGB. |
x_dither | X offset for dither. |
y_dither | Y offset for dither. |

### gdk_pixbuf_render_pixmap_and_mask ()

    void
    gdk_pixbuf_render_pixmap_and_mask (GdkPixbuf *pixbuf,
                                       GdkPixmap **pixmap_return,
                                       GdkBitmap **mask_return,
                                       int alpha_threshold);

Creates a pixmap and a mask bitmap which are returned in the `pixmap_return` and `mask_return` arguments, respectively, and renders a pixbuf and its corresponding thresholded alpha mask to them. This is merely a convenience function; applications that need to render pixbufs with dither offsets or to given drawables should use `gdk_draw_pixbuf()` and `gdk_pixbuf_render_threshold_alpha()`.

The pixmap that is created is created for the colormap returned by `gdk_rgb_get_colormap()`. You normally will want to instead use the actual colormap for a widget, and use `gdk_pixbuf_render_pixmap_and_mask_for_colormap()`.

If the pixbuf does not have an alpha channel, then *`mask_return` will be set to `NULL`.

#### Parameters

pixbuf | A pixbuf. |
pixmap_return | Location to store a pointer to the created pixmap, or `NULL` if the pixmap is not needed. |
mask_return | Location to store a pointer to the created mask, or `NULL` if the mask is not needed. |
alpha_threshold | Threshold value for opacity values. |

### gdk_pixbuf_render_pixmap_and_mask_for_colormap ()

    void
    gdk_pixbuf_render_pixmap_and_mask_for_colormap
                                   (GdkPixbuf *pixbuf,
                                    GdkColormap *colormap,
                                    GdkPixmap **pixmap_return,
                                    GdkBitmap **mask_return,
                                    int alpha_threshold);

`gdk_pixbuf_render_pixmap_and_mask_for_colormap` is deprecated and should not be used in newly-written code.

Creates a pixmap and a mask bitmap which are returned in the `pixmap_return` and `mask_return` arguments, respectively, and renders a pixbuf and its corresponding tresholded alpha mask to them. This is merely a convenience function; applications that need to render pixbufs with dither offsets or to given drawables should use `gdk_draw_pixbuf()`, and `gdk_pixbuf_render_threshold_alpha()`.

The pixmap that is created uses the GdkColormap specified by `colormap` . This colormap must match the colormap of the window where the pixmap will eventually be used or an error will result.

If the pixbuf does not have an alpha channel, then *`mask_return` will be set to `NULL`.

#### Parameters

pixbuf | A pixbuf. |
colormap | A GdkColormap |
pixmap_return | Location to store a pointer to the created pixmap, or `NULL` if the pixmap is not needed. |
mask_return | Location to store a pointer to the created mask, or `NULL` if the mask is not needed. |
alpha_threshold | Threshold value for opacity values. |

### gdk_pixbuf_get_from_drawable ()

    GdkPixbuf *
    gdk_pixbuf_get_from_drawable (GdkPixbuf *dest,
                                  GdkDrawable *src,
                                  GdkColormap *cmap,
                                  int src_x,
                                  int src_y,
                                  int dest_x,
                                  int dest_y,
                                  int width,
                                  int height);

Transfers image data from a GdkDrawable and converts it to an RGB(A) representation inside a GdkPixbuf. In other words, copies image data from a server-side drawable to a client-side RGB(A) buffer. This allows you to efficiently read individual pixels on the client side.

If the drawable `src` has no colormap (`gdk_drawable_get_colormap()` returns `NULL`), then a suitable colormap must be specified. Typically a GdkWindow or a pixmap created by passing a GdkWindow to `gdk_pixmap_new()` will already have a colormap associated with it. If the drawable has a colormap, the `cmap` argument will be ignored. If the drawable is a bitmap (1 bit per pixel pixmap), then a colormap is not required; pixels with a value of 1 are assumed to be white, and pixels with a value of 0 are assumed to be black. For taking screenshots, `gdk_colormap_get_system()` returns the correct colormap to use.

If the specified destination pixbuf `dest` is `NULL`, then this function will create an RGB pixbuf with 8 bits per channel and no alpha, with the same size specified by the `width` and `height` arguments. In this case, the `dest_x` and `dest_y` arguments must be specified as 0. If the specified destination pixbuf is not `NULL` and it contains alpha information, then the filled pixels will be set to full opacity (alpha = 255).

If the specified drawable is a pixmap, then the requested source rectangle must be completely contained within the pixmap, otherwise the function will return `NULL`. For pixmaps only (not for windows) passing -1 for width or height is allowed to mean the full width or height of the pixmap.

If the specified drawable is a window, and the window is off the screen, then there is no image data in the obscured/offscreen regions to be placed in the pixbuf. The contents of portions of the pixbuf corresponding to the offscreen region are undefined.

If the window you're obtaining data from is partially obscured by other windows, then the contents of the pixbuf areas corresponding to the obscured regions are undefined.

If the target drawable is not mapped (typically because it's iconified/minimized or not on the current workspace), then `NULL` will be returned.

If memory can't be allocated for the return value, `NULL` will be returned instead.

(In short, there are several ways this function can fail, and if it fails it returns `NULL`; so check the return value.)

This function calls `gdk_drawable_get_image()` internally and converts the resulting image to a GdkPixbuf, so the documentation for `gdk_drawable_get_image()` may also be relevant.

#### Parameters

dest | Destination pixbuf, or `NULL` if a new pixbuf should be created. | [allow-none]
src | Source drawable. |
cmap | A colormap if `src` doesn't have one set. |
src_x | Source X coordinate within drawable. |
src_y | Source Y coordinate within drawable. |
dest_x | Destination X coordinate in pixbuf, or 0 if `dest` is NULL. |
dest_y | Destination Y coordinate in pixbuf, or 0 if `dest` is NULL. |
width | Width in pixels of region to get. |
height | Height in pixels of region to get. |

#### Returns

The same pixbuf as `dest` if it was non-`NULL`, or a newly-created pixbuf with a reference count of 1 if no destination pixbuf was specified, or `NULL` on error

### gdk_pixbuf_get_from_image ()

    GdkPixbuf *
    gdk_pixbuf_get_from_image (GdkPixbuf *dest,
                               GdkImage *src,
                               GdkColormap *cmap,
                               int src_x,
                               int src_y,
                               int dest_x,
                               int dest_y,
                               int width,
                               int height);

Same as `gdk_pixbuf_get_from_drawable()` but gets the pixbuf from an image.

#### Parameters

dest | Destination pixbuf, or `NULL` if a new pixbuf should be created. | [allow-none]
src | Source GdkImage. |
cmap | A colormap, or `NULL` to use the one for `src` . | [allow-none]
src_x | Source X coordinate within drawable. |
src_y | Source Y coordinate within drawable. |
dest_x | Destination X coordinate in pixbuf, or 0 if `dest` is NULL. |
dest_y | Destination Y coordinate in pixbuf, or 0 if `dest` is NULL. |
width | Width in pixels of region to get. |
height | Height in pixels of region to get. |

#### Returns

`dest` , newly-created pixbuf if `dest` was `NULL`, `NULL` on error

## Types and Values