 Bitmap: A bitmap is a rectangular array of 0s and 1s that serves as a drawing mask for a corresponding rectangular portion of the window.  Applications: The most application of bitmaps in OpenGL is to display Fonts on the screen.  Raster Position: Points to a location on the screen where the bitmap is drawn(Lower Left Corner). Note: Raster Position is affected by MODEL_VIEW matrix  Use glRasterPos to set Raster Position

 Drawing Bitmaps: ◦ First setup the position that you want to draw using glRasterPos2i(x, y). ◦ Then use glBitmap as follow to draw the bitmap: glBitmap(width, height, xbo, ybo, xbi, ybi, const GLubyte *bitmap)

 Display lists are very useful when used with fonts.  A new list can be generated for each character and be called correspondingly when needed.  By using display lists, you can define a function that takes a text as input and prints out the input on screen.

 Reading, Writing, and Copying Pixel: ◦ Use three basic commands that manipulate image data  glReadPixels() - Reads a rectangular array of pixels from the framebuffer and stores the data in processor memory.  glDrawPixels() - Writes a rectangular array of pixels from data kept in processor memory into the framebuffer at the current raster position specified by glRasterPos*().  glCopyPixels() - Copies a rectangular array of pixels from one part of the framebuffer to another. This command behaves similarly to a call to glReadPixels() followed by a call to glDrawPixels(), but the data is never written into processor memory.

 glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels) Reads pixel data from the framebuffer rectangle whose lower-left corner is at (x, y) and whose dimensions are width and height and stores it in the array pointed to by pixels. Note: If you are using double-buffer, you have to specify which buffer are you using front buffer or back buffer.

 void glDrawPixels(GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid *pixels) Draws a rectangle of pixel data with dimensions width and height. The pixel rectangle is drawn with its lower-left corner at the current raster position. format and type have the same meaning as with glReadPixels(). Note: If the current raster position is invalid, nothing is drawn, and the raster position remains invalid.

 Packing and unpacking refer to the way that pixel data is written to and read from processor memory.  During Packing and Unpacking, we are enable to manipulate the data read.  Such modifications consist of: ◦ Controlling Pixel-Storage Modes ◦ Pixel-Transfer Operations ◦ Pixel Mapping

 Packing and unpacking refer to the way that pixel data is written to and read from processor memory.  Sometimes you may be dealing with packing/unpacking a sub-image instead of the whole image.  In such conditions, controlling byte alignment may be very useful: ◦ Different machines have different byte orders ◦ Some machines have special hardware that works only if data is aligned in 2, 4 or 8 byte boundaries in processor memory. ◦ In such cases, we use glPixelStore to align the data

 Before the data is written to frame-buffer or processor memory, OpenGL can perform several operations on it.  The range of a component can be changed, e.g. you may want to change the range of red component to be other than [0,1]  Or, could be that the data you are using comes from a different graphic system which stores the RGB components in a different range rather than [0,1]  In these situations use glPixelTransfer function in order to transform the data as you need.

QUESTIONS?