Editing Bit blit (section)

==Blitting vs hardware sprites==
{{See also|Sprite (computer graphics)}}

Blitting is similar to hardware-[[Sprite (computer graphics)|sprite]] drawing, in that both systems reproduce a pattern, typically a square area, at different locations on the screen.<ref>{{cite web |title=Framebuffer - OpenGL Wiki |url=https://www.khronos.org/opengl/wiki/Framebuffer#Blitting |website=www.khronos.org |accessdate=23 June 2020 |quote=A blit operation is a special form of copy operation; it copies a rectangular area of pixels from one framebuffer to another. This function also has some very specific properties with regard to multisampling.}}</ref> Hardware sprites have the advantage of being stored in separate memory, and therefore don't disturb the main display memory. This allows them to be moved about the display, covering the "background", with no effect on it.

Blitting moves the same types of patterns about the screen, but does so by writing into the same memory as the rest of the display. This means that every time a foreground pattern is placed on the screen, any background pixels underneath it are overwritten, or "damaged". It is up to the software to repair this damage by blitting twice, once to restore the pixels that were changed, and then again to place the foreground pattern in its new location. One way to do it is to store the required patterns in VRAM offscreen and to reserve another area offscreen as a sort of stack to temporarily store the affected display section. Assuming the graphics chip has dedicated VRAM this is useful to lessen the strain on system RAM but also the bandwidth limited ISA expansion slot on older PC systems. 

However, there are several ways to optimize this. If large areas of the screen are taken over by the patterns, it may be more efficient to blit the background to the screen instead of erasing each pattern individually. A variation involves dividing the screen into segments and erasing only the segments where patterns have been drawn on. This technique is known as dirty rectangles.