Question

6 Procedure 1. Download the skeleton project: $ cd cs103 ş mkdir chromakey s cd chromakey s wget http://bits.usc.edu/files/cs103/chromakey/cs103_chromakey.tar ş tar xvf cs103_chromakey.tar This will download the files: chromakey.cpp [Source code skeleton for you to complete] bmplib.h bmplib.cpp Makefile colbert gs.bmp bird gs.bmp header file for you to include in chromakey.cpp] [Source code containing the .bmp read/write functions] [Script for you to compile your program] astro.bmp faded.bmp Green-screened images for you to test with] campus1.bmp village.bmp [Background images] readme.txt [readme template for pre-lab and review, to submit] 2. Edit the chromakey.cpp file taking note of the comments embedded in it. You will implement two different methods. In addition to prototypes for the methods already mentioned, in main() we provide some starter code. When calling the read and write BMP file functions, note that we check the return value to ensure successful operation. If one of these functions ever returns a non-zero value, exit the program immediately using "return 1;". Look up the cmath library functions to take the power of a number and the square root. This is useful for computing RGB distance. 3. Review how to pass an array to a function. You will need this when you write your calls to method1(), method2(), and replace() 4. 5. For method 1 you must implement the distance method described earlier in the lab. First determine which set of pixels (location of pixels) you will "assume" are background in any green-screen image. You should write code to iterate over these and find the "chromakey" (average R, G, B) values. Then iterate over the entire image computing the distance between each pixel and the chromakey value, and setting the mask array appropriately. Use the distance threshold that the user entered at the command line. You will need to determine a good threshold value by repeatedly re-running your program and examining the resulting output1.bmp (or colbert1.bmp / bird1.bmp) file 6. At this point you can complete the replace() function and main() function, test whether your method1 worked, and see the effects of different distance thresholds.