feat(filter): add pixelate (-P flag) for mosaic effect

Author: swastijain132005

README.md

@@ -181,6 +181,21 @@ Gx
 
 The result is clamped between 0 and 255 and replaces the original pixel value. This produces a monochrome image where edges are highlighted, giving a pencil-sketch effect.
 
+
+
+### Pixelate Filter
+
+The “Pixelate” filter divides the image into small square blocks (default 5x5) and replaces each block with the average color of its pixels. This creates a mosaic-like effect, useful for artistic rendering or obscuring parts of an image for privacy.
+
+Algorithm Steps:
+
+1. Divide the image into blocks of size blockSize x blockSize.
+2. For each block:
+   a. Compute the average Red, Green, and Blue values of all pixels in the block.
+   b. Replace all pixels in the block with the computed average color.
+3. Repeat until all blocks are processed.
+
+
 ---
 
 ### Usage

filter.c

@@ -7,7 +7,7 @@
 int main(int argc, char *argv[])
 {
     // Define allowable filters
-    char *filters = "bgrsivtd";
+    char *filters = "bgrsivtdp";
 
 
 
@@ -134,6 +134,12 @@ while ((opt = getopt(argc, argv, filters)) != -1)
     detect_edges(height, width, image);
     break;
 
+
+
+    case 'p':
+    apply_pixelate(height, width, image, 5); // default block size = 5
+    break;
+
       default:
     printf("Unknown filter: %c\n", filterArr[i]);
     free(image);

helpers.c

@@ -270,6 +270,59 @@ void detect_edges(int height, int width, RGBTRIPLE image[height][width])
         }
     }
 
+
+
+// Pixelate Filter
+void apply_pixelate(int height, int width, RGBTRIPLE image[height][width], int blockSize)
+{
+    for (int i = 0; i < height; i += blockSize)
+    {
+        for (int j = 0; j < width; j += blockSize)
+        {
+            int sumRed = 0, sumGreen = 0, sumBlue = 0;
+            int count = 0;
+
+            // Compute average color in the block
+            for (int bi = 0; bi < blockSize; bi++)
+            {
+                for (int bj = 0; bj < blockSize; bj++)
+                {
+                    int ni = i + bi;
+                    int nj = j + bj;
+                    if (ni < height && nj < width)
+                    {
+                        sumRed += image[ni][nj].rgbtRed;
+                        sumGreen += image[ni][nj].rgbtGreen;
+                        sumBlue += image[ni][nj].rgbtBlue;
+                        count++;
+                    }
+                }
+            }
+
+            int avgRed = sumRed / count;
+            int avgGreen = sumGreen / count;
+            int avgBlue = sumBlue / count;
+
+            // Set all pixels in the block to the average color
+            for (int bi = 0; bi < blockSize; bi++)
+            {
+                for (int bj = 0; bj < blockSize; bj++)
+                {
+                    int ni = i + bi;
+                    int nj = j + bj;
+                    if (ni < height && nj < width)
+                    {
+                        image[ni][nj].rgbtRed = avgRed;
+                        image[ni][nj].rgbtGreen = avgGreen;
+                        image[ni][nj].rgbtBlue = avgBlue;
+                    }
+                }
+            }
+        }
+    }
+}
+
+
     // Free temporary array
     for (int i = 0; i < height; i++)
         free(copy[i]);

helpers.h

@@ -29,4 +29,8 @@ void threshold(int height, int width, RGBTRIPLE image[height][width]);
 // **New: Edge Detection filter**
 void detect_edges(int height, int width, RGBTRIPLE image[height][width]);
 
+// Pixelate filter
+void apply_pixelate(int height, int width, RGBTRIPLE image[height][width], int blockSize);
+
+
 #endif