glBitmap(3G) OpenGL Reference 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 GLBITMAP and format set
to GLCOLORINDEX. 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 = | x - x |
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glBitmap(3G) OpenGL Reference glBitmap(3G)
y = | y - y |
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where (x ,y ) is the raster position and (x ,y ) is the bitmap origin.
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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 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 viewport.
ERRORS
GLINVALIDVALUE is generated if width or height is negative.
GLINVALIDOPERATION is generated if glBitmap is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLCURRENTRASTERPOSITION
glGet with argument GLCURRENTRASTERCOLOR
glGet with argument GLCURRENTRASTERINDEX
glGet with argument GLCURRENTRASTERTEXTURECOORDS
glGet with argument GLCURRENTRASTERPOSITIONVALID
SEE ALSO
glDrawPixels, glPixelStore, glPixelTransfer, glRasterPos
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