GLBITMAP() MachTen Programmer’s Manual GLBITMAP()

NAME
glBitmap - draw a bitmap

C SPECIFICATION
void glBitmap( GLsizei width,
GLsizei height,
GLfloat xorig,
GLfloat yorig,
GLfloat xmove,
GLfloat ymove,
const GLubyte *bitmap )

delim $$

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

$ x sub w ~=~ | ~ x sub r ~-~ x sub o ~ | $

$ y sub w ~=~ | ~ y sub r ~-~ y sub o ~ | $

where $ ( x sub r , y sub r ) $ is the raster position and
$ ( x sub o , y sub o ) $ is the bitmap origin. Fragments
are then generated for each pixel corresponding to a 1
(one) in the bitmap image. These fragments are generated
using the current raster z coordinate, color or color
index, and current raster texture coordinates. 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 cur-
rent raster position, or to the current raster color, tex-
ture 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
viewport.

ERRORS
GL_INVALID_VALUE is generated if width or height is nega-
tive.

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_INDEX
glGet with argument GL_CURRENT_RASTER_TEXTURE_COORDS
glGet with argument GL_CURRENT_RASTER_POSITION_VALID

SEE ALSO
glDrawPixels, glPixelStore, glPixelTransfer, glRasterPos

MachTen 2