MIPS Graphics Library


The reason for this task is twofold: first it helped show me show much work the processor had to do to display a simple shape on the screen; it also taught me memory management.

The program was written in MARS virtual environment, and uses the Bitmap display to give a visual representation of the code. Each method uses 4 memory addresses to pass parameters, if any more are needed then they are sent to the stack. 

The “SetPixel” method is the simplest, it takes the X, Y and colour of the pixel – calculates it position on the screen and then stores the colour into the memory address into the location where the screen gets its information. 

The “DrawLine” method uses Bresenham’s Line algorithm. It takes a start point and end point of the line as parameters, as well as the colour. It then works out the gradient of the line, plots the first pixel, and then adds the gradient again to get to the next pixel. This repeats until it has reached the second point.

The “DrawRectangle” and “DrawPolygon” methods work in the same way except they calculate where the lines need to be, before calling the “DrawLine” method. I have also implemented a “FillRectangle” method which simply draws a line from one side to the other.

Finally I also included “DrawCircle” and “FillCircle” routines, these both use the Midpoint Circle Algorithm. “DrawCircle” plots 8 points at a time around the circle, calculated by getting the radius and position of the midpoint; the 8 points then draw 45 degrees of the circle each, until they meet and form a complete circle. The “FillCircle” routine is similar, but instead of plotting 8 points, takes 4 points as start parameters and 4 points as end parameters, which are then passed into “DrawLine”.


If you would like to download the source code, it is available here | 22 KB

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