Add threshold filter (-t flag), update documentation and filter logic

Author: saumya1317

README.md

@@ -113,6 +113,16 @@ For a pixel along the edge or corner, like pixel 15, we would still look for all
 
 If you apply the above algorithm to each pixel in the image, the result should look like a blurry, out-of-focus version of the original.
 
+### 5.) Threshold Filter (Black & White)
+
+- **Flag:** `-t`
+- **Description:** Converts each pixel in the image to pure black or white based on its intensity. If the average of red, green, and blue is greater than or equal to 128, the pixel becomes white (255,255,255); otherwise, it becomes black (0,0,0).
+- **Usage example:**
+
+```sh
+./filter -t input.bmp output.bmp
+```
+
 You should not modify any of the function signatures, nor should you modify any other files other than helpers.c.
 
 Consider the following grid of pixels, where we’ve numbered each pixel.

filter.c

@@ -7,7 +7,7 @@
 int main(int argc, char *argv[])
 {
     // Define allowable filters
-    char *filters = "bgrsi";
+    char *filters = "bgrsit";
 
 
     char filterArr[argc-3];
@@ -125,6 +125,11 @@ int main(int argc, char *argv[])
         case 'i':
             invert(height,width,image);
             break;
+
+        // Threshold (black & white)
+        case 't':
+            threshold(height, width, image);
+            break;
         default:
             printf("%c", &filterArr[i]);
             break;

helpers.c

@@ -66,4 +66,21 @@ void blur(int height, int width, RGBTRIPLE image[height][width]){
 
 // Blur image
 
+}
+
+void threshold(int height, int width, RGBTRIPLE image[height][width]){
+    for(int i = 0; i < height; i++){
+        for(int j = 0; j < width; j++){
+            int avg = (image[i][j].rgbtRed + image[i][j].rgbtGreen + image[i][j].rgbtBlue) / 3;
+            if (avg >= 128) {
+                image[i][j].rgbtRed = 255;
+                image[i][j].rgbtGreen = 255;
+                image[i][j].rgbtBlue = 255;
+            } else {
+                image[i][j].rgbtRed = 0;
+                image[i][j].rgbtGreen = 0;
+                image[i][j].rgbtBlue = 0;
+            }
+        }
+    }
 }

helpers.h

@@ -14,3 +14,6 @@ void reflect(int height, int width, RGBTRIPLE image[height][width]);
 
 // Blur image
 void blur(int height, int width, RGBTRIPLE image[height][width]);
+
+// Threshold filter (black and white)
+void threshold(int height, int width, RGBTRIPLE image[height][width]);