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1.13 class bitmap

A bitmap is a graphical that displays an image. Most of the behaviour to manipulate the pixels of a bitmaps thus can be found with class image.

Bitmaps (images) come in two flavours. If image<-kind = bitmap, the elements of the bitmap are regarded as booleans: boolean true (@on) is painted in the graphical<-colour of the bitmap and boolean false (@off) in the current background. If image<-kind is pixmap each individual pixel represents a colour.

Transparency comes from the image rather than from the bitmap: pixels that the image's alpha channel calls transparent are not painted, and the bitmap lets whatever is behind it show through. Use image->has_alpha to test whether an image has such pixels. Older versions had a bitmap<->transparent to say that the @off pixels of a bitmap-kind image should not be painted, and took it as the second argument of bitmap->initialise; both are gone.

Bugs:

Stencils are not implemented.

There are no means for scaling bitmaps: bitmap->geometry moves a bitmap but ignores the requested size. Scale the image instead, with image<-scale.

See also
- class image
- bitmap-status

1.13.1 Instance variables

bitmap <- image: image
The image that contains the actual pixels.

1.13.2 Send methods

bitmap ->geometry: x=[int], y=[int], width=[int], height=[int]
Just moves the bitmap. In the current implementation bitmaps cannot be scaled.
bitmap ->image: image
Associate an image with a bitmap. Sets the width and height of the bitmap to the width and height of the image. If the image has bitmap<->access both and bitmap<->bitmap @nil, the bitmap<->bitmap variable of the image is filled with the bitmap. Subsequent changes to the image are forwarded to the bitmap.
See also
image-bitmap
bitmap ->initialise: image=[image]
Create a bitmap for the given image object. The bitmap will be given the same graphical<-width and graphical<-height as the image.

Note that images are automatically converted from names (see image->initialise). Thus, the following displays XPCE's icon on a picture window: 

?- send(new(P, picture), open),
   send(P, display,
            bitmap('16x16/pce.xpm'), point(25, 25)).

By default, image objects are cached (i.e. remain in memory). If you have many or large ones, please study image->initialise and image->load.

bitmap ->load: file, path=[char_array]
Load file in the associated image. XPCE searches for the file in the path described by the last argument. The default path is image.path.

Backward compatibility only. New code should manipulate the image directly.

Defaults: The default search path is determined by the resource bitmap.path. Its system defined value is 

.:~/lib/bitmaps:$PCEHOME/bitmaps:/usr/include/X11/bitmaps

Diagnostics: Fails silently on bad format or non-existing file.

See also
image->save

1.13.3 Get methods

bitmap <-contains: -> chain
Return a new chain object holding bitmap<-image.
bitmap <-convert: name -> bitmap
bitmap<-convert converts text of the form