Question

lab3RGB.c file:

#include <stdio.h>

#define AlphaValue 100


int main() {

  int r, g,b;
  unsigned int rgb_pack;
  int r_unpack, g_unpack,b_unpack;
  int alpha = AlphaValue;

  printf("enter R value (0~255): ");
  scanf("%d",&r);
  printf("enter G value (0~255): ");
  scanf("%d",&g);
  printf("enter B value (0~255): ");
  scanf("%d",&b);

  while(! (r<0 || g<0 || b <0) )
  {             
     printf("A: %d\t", alpha);  printBinary(alpha); printf("\n");
     printf("R: %d\t", r);  printBinary(r); printf("\n");
     printf("G: %d\t", g);  printBinary(g); printf("\n"); 
     printf("B: %d\t", b);  printBinary(b); printf("\n"); 

    /* do the packing */






     //printf("\nPacked: value %d\t", rgb_pack); printBinary(rgb_pack);printf("\n");
     printf("\nPacked:\t"); printBinary(rgb_pack);printf(" (%d)\n", rgb_pack);
     printf("\nUnpacking  ......\n");

    /* do unpacking */






     printf("R: "); printBinary(r_unpack); printf(" (%d, %#o, %#X)\n", r_unpack, r_unpack, r_unpack);
     printf("G: "); printBinary(g_unpack); printf(" (%d, %#o, %#X)\n", g_unpack, g_unpack, g_unpack);
     printf("B: "); printBinary(b_unpack); printf(" (%d, %#o, %#X)\n", b_unpack, b_unpack, b_unpack);
     printf("------------------------------------\n"); 
         
     /* read again */
     printf("\nenter R value: ");
     scanf("%d",&r);
     printf("enter G value: ");
     scanf("%d",&g);
     printf("enter B value: ");
     scanf("%d",&b);

  }

}

7. Problem D2 Bitwise operation 7.1 Specification A digital image is typically stored in computer by means of its pixel values, as well as some formatting information. Each pixel value consists of 3 values of 0 255, representing red (R) green (G) and blue (B) As mentioned in class, Java's BufferedImage class has a method int getRGB (int x, İnt y), which allows you to retrieve the RGB value of an image at pixel position (x,y). How could the method return 3 values at a time? As mentioned in class, the 'trick' is to return an integer (32 bits) that packs the 3 values into it. Since each value is 0255 thus 8 bit is enough to represent it, an 32 bits integer has sufficient bits. They are packed in such a way that, counting from the right most bit, B values occupies the first 8 bits (bit 07), G occupies the next 8 bits, and R occupies the next 8 bits. This is shown below. (The left-most 8 bits is packed with some other information about the image, called Alpha, which we are not interested here.) 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 987 6 5 4 3 210 Suppose a pixel has R value 2 (which is binary 00000010), G value 7 (which is binary 00000111) and B value 8 (which is binary 00001000), and Alpha has value 100, then the integer is packed as 100 for Alpha 7.2 Implementation In this exercise, you are going to use bitwise operations to pack input R,G and B values into an integer, and then use bitwise operations again to unpack the packed integer to retrieve the R, G and B values. Download and complete lab3RGB.c. This C program keeps on reading input from the stdin. Each input contains 3 integers representing the R, G and B value respectively, and then outputs the 3 values with their binary representations. The binary fepresentations are generated by calling function void printBinary (int val), which is defined for you in another program binaryFunction.c. (How do you use a function that is defined in another file? Don't include) Next is the pack part that you should implement. This packs the 3 input values, as well as Alpha value which is assumed to be 100, into integer variable rgb_pack. Then the value of rgb_pack and its binary representation is displayed (implemented for you) Next you should unpack the R, G and B value from the packed integer rgb_pack. After that, the unpacked R,G and B value and their Binary, Octal and Hex representations are displayed (implemented for you) The program terminates when you enter a negative number for either R, G or B value Hint: Packing might be a little easier than unpacking. Considering shifting R,G,B values to the proper positions and then somehow merge them into one integer (using bitwise operators). For unpacking, you can either do shifting masking, or, masking + shifting, or, shifting only. Shifting ackedi binay: 011010 011113 100 1000 Unpacking R: binary: 00000000 00000000 00000000 01111011 (123, 0173, 0X7B) G: binary: 00000000 00000000 00000000 11100000 (224, 0340, 0XEO) B: binary: 00000000 00000000 00000000 10000011 (131, 0203, 0x83) enter R value: 254 enter G value: 123 enter B value: 19 A: 100 binary: 00000000000000000000000001100100 R: 254 binary: 00000000 00000000 00000000 11111110 G: 123 binary: 00000000 00000000 00000000 01111011 B: 19 binary: 00000000 00000000 00000000 00010011 Unpacking R: binary: 00000000 00000000 00000000 11111110 (254, 0376, 0XFE) G: binary: 00000000 00000000 00000000 01111011 (123, 0173, 0X7B) B: binary: 00000000 00000000 00000000 00010011 19, 023, 0X13) enter R value: -3 enter G value:3 enter B value: 56 red 340 % Assume all the inputs are valid.

Answer 1

• I have pasted the code and screenshot of successful run below.
• In case of any doubts just comment down.

-------------------------Screenshot-----------------------

ksmukta:10.c->gcc a.c &&./a.out enter R value (0-255): 254 enter G value (0-255): 123 enter B value (0-255): 19 A: 100 00000000 00000000 00000000 01100106 R: 254 00000000 00000000 00000000 11111116 G: 123 00000000 00000000 00000000 01111011 B: 1900000000 00000000 00000000 00010011 R: 00000000 00000000 00000000 11111110 (254, 0376, θχFE) G: 00000000 00000000 00000000 θ1111011 (123 , 0173, θΧ7B) B: 00000000 00000000 00000000 00010011 (19, θ23, θΧ13) enter R value: C ksmukta:10.c ->

-------------------------Code-----------------------

#include <stdio.h>
#define AlphaValue 100

void printBinary(int a){
char binary[33];
for(int i=31;i>=0;i--){
binary[i] = '0'+(a%2);
a/=2;
}
binary[32] = '\0';
for(int i=0;i<32;i++){
printf("%c",binary[i]);
if(i>0 && ((i+1)%8==0) && i!= 31) printf(" ");
}
}

int main() {

int r, g,b;
unsigned int rgb_pack;
int r_unpack, g_unpack,b_unpack;
int alpha = AlphaValue;

printf("enter R value (0~255): ");
scanf("%d",&r);
printf("enter G value (0~255): ");
scanf("%d",&g);
printf("enter B value (0~255): ");
scanf("%d",&b);

while(! (r<0 || g<0 || b <0) )
{   
printf("A: %d\t", alpha); printBinary(alpha); printf("\n");
printf("R: %d\t", r); printBinary(r); printf("\n");
printf("G: %d\t", g); printBinary(g); printf("\n");
printf("B: %d\t", b); printBinary(b); printf("\n");

/* do the packing */
rgb_pack = 0;
rgb_pack = rgb_pack | (alpha<<24);
rgb_pack = rgb_pack | (r<<16);
rgb_pack = rgb_pack | (g<<8);
rgb_pack = rgb_pack | (b<<0);

//printf("\nPacked: value %d\t", rgb_pack); printBinary(rgb_pack);printf("\n");
printf("\nPacked:\t"); printBinary(rgb_pack);printf(" (%d)\n", rgb_pack);
printf("\nUnpacking ......\n");

/* do unpacking */

int rmask = ((1<<8)-1)<<16;
r_unpack = (rgb_pack & rmask)>>16;
int gmask = ((1<<8)-1)<<8;
g_unpack = (rgb_pack & gmask)>>8;
int bmask = ((1<<8)-1)<<0;
b_unpack = (rgb_pack & bmask)>>0;

printf("R: "); printBinary(r_unpack); printf(" (%d, %#o, %#X)\n", r_unpack, r_unpack, r_unpack);
printf("G: "); printBinary(g_unpack); printf(" (%d, %#o, %#X)\n", g_unpack, g_unpack, g_unpack);
printf("B: "); printBinary(b_unpack); printf(" (%d, %#o, %#X)\n", b_unpack, b_unpack, b_unpack);
printf("------------------------------------\n");

/* read again */
printf("\nenter R value: ");
scanf("%d",&r);
printf("enter G value: ");
scanf("%d",&g);
printf("enter B value: ");
scanf("%d",&b);

}

}