This will be the fourth assignment using ARMv7 assembly language in the VisUAL emulator. 0

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This will be the fourth assignment using ARMv7 assembly language in the VisUAL emulator. 0

When we write a program to display graphics, we often need to convert an analog, floating-point number into a decimal number. A computer display is an array of structures, one for each dot on the display, and these dots are called pixels. Each pixel has a combination of numbers which describe the color of the pixel. These are usually a 32-bit structure, comprising one byte each for the colors red, green, and blue, plus one byte for transparency or opacity. This is generically called an RGB triplet, RGB value, 24- or 32-bit color, or other names.

 

(There are several other computer display color systems, and not all are restricted to 24 bits of color, but that is outside our purpose here.)The array where your image is displayed is indexed by integer values, termed x and y (as in Cartesian coordinates). So, if we are charting some formula like x2-x, we have to convert the output from analog to digital so we can select the appropriate pixel to color to graph the formula.

 

But if we are plotting a straight line, we have to compute which pixels to color. The method we use is called Bresenham's algorithm. The Wikipedia article on this is a good enough reference.

 

The Assignment You are to write a subroutine using the VisUAL emulator which implements Bresenham's algorithm. Your program will receive two pairs of coordinate locations; these will be in registers 1 through 4, representing variables called x1, y1, x2, and y2. The stack will serve as a storage area where you will place the coordinates of the pixels which must be colored in to complete a line from (x1,y1) to (x2,y2). (This is not standard practice.) The coordinates will each be a pair of words, which we will call xi   and yi   respectively.  You should call your subroutine L6.

 

The logic to implement Bresenham's algorithm in C++ is available at:

https://justtechreview.com/bresenhams-line-drawing-algorithm-in-c-and-c/Links to an external site.

 

This example uses a subroutine named putpixel. In lieu of having that subroutine available to us, please store your x and y values with the following code:

 

STR Rx,[SP] SUB SP,#4 STR Ry,[SP] SUB SP,#4

 

This will create an array of values.You may assume that the input values are correct - no negative values, et cetera, and all in a range of zero to 256.

 

GradingThe following standard will be used for grading:Successful assembly and execution with no error messages: 8 pointsCorrect output for the starting point: 4Correct output for the ending point: 4Correct output for the line between the starting and ending point: 24Your program should include the following line at the beginning:Points will be deducted if this is missing or incorrect. "Last, first" is your name, and "nnnnn" is your section number

 

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