GLBITMAP(3G) GLBITMAP(3G)
NAME
glBitmap - draw a bitmap
C SPECIFICATION
void glBitmap( GLsizei width,
GLsizei height,
GLfloat xorig,
GLfloat yorig,
GLfloat xmove,
GLfloat ymove,
const GLubyte *bitmap )
PARAMETERS
width, height Specify the pixel width and height of the bitmap image.
xorig, yorig Specify the location of the origin in the bitmap image. The origin is measured from
the lower left corner of the bitmap, with right and up being the positive axes.
xmove, ymove Specify the x and y offsets to be added to the current raster position after the bitmap
is drawn.
bitmap Specifies the address of the bitmap image.
DESCRIPTION
A bitmap is a binary image. When drawn, the bitmap is positioned relative to the current raster
position, and frame buffer pixels corresponding to 1's in the bitmap are written using the current
raster color or index. Frame buffer pixels corresponding to 0's in the bitmap are not modified.
glBitmap takes seven arguments. The first pair specifies the width and height of the bitmap image.
The second pair specifies the location of the bitmap origin relative to the lower left corner of the
bitmap image. The third pair of arguments specifies x and y offsets to be added to the current
raster position after the bitmap has been drawn. The final argument is a pointer to the bitmap image
itself.
The bitmap image is interpreted like image data for the glDrawPixels command, with width and height
corresponding to the width and height arguments of that command, and with type set to GL_BITMAP and
format set to GL_COLOR_INDEX. Modes specified using glPixelStore affect the interpretation of bitmap
image data; modes specified using glPixelTransfer do not.
If the current raster position is invalid, glBitmap is ignored. Otherwise, the lower left corner of
the bitmap image is positioned at the window coordinates
xw = xr - xo
yw = yr - yo
where ( xr , yr ) is the raster position and ( xo , yo ) is the bitmap origin. Fragments are then
generated for each pixel corresponding to a 1 (one) in the bitmap image. These fragments are gener-ated generated
ated using the current raster z coordinate, color or color index, and current raster texture coordi-nates. coordinates.
nates. They are then treated just as if they had been generated by a point, line, or polygon,
including texture mapping,
fogging, and all per-fragment operations such as alpha and depth testing.
After the bitmap has been drawn, the x and y coordinates of the current raster position are offset by
xmove and ymove. No change is made to the z coordinate of the current raster position, or to the
current raster color, texture coordinates, or index.
NOTES
To set a valid raster position outside the viewport, first set a valid raster position inside the
viewport, then call glBitmap with NULL as the bitmap parameter and with xmove and ymove set to the
offsets of the new raster position. This technique is useful when panning an image around the view-port. viewport.
port.
ERRORS
GL_INVALID_VALUE is generated if width or height is negative.
GL_INVALID_OPERATION is generated if glBitmap is executed between the execution of glBegin and the
corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GL_CURRENT_RASTER_POSITION
glGet with argument GL_CURRENT_RASTER_COLOR
glGet with argument GL_CURRENT_RASTER_DISTANCE
glGet with argument GL_CURRENT_RASTER_INDEX
glGet with argument GL_CURRENT_RASTER_TEXTURE_COORDS
glGet with argument GL_CURRENT_RASTER_POSITION_VALID
SEE ALSO
glDrawPixels(3G), glPixelStore(3G), glPixelTransfer(3G), glRasterPos(3G)
GLBITMAP(3G)
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