Codebrawl #2 Víctor Pimentel Gist

output.png

solution.rb

#!/usr/bin/env ruby

require 'chunky_png'

image = ChunkyPNG::Image.from_file('input.png')

# Size of the blocks in pixels by pixels
blockSize = 10

# Process block by block
w = 0
while w < image.width do
  h = 0
  while h < image.height do
    sum = [0, 0, 0] # Sum of all the rgb values of the pixels in the block
    pixels = 0 # Number of pixels in the block (blocks at the right/bottom may be incomplete)
    avg = [0, 0, 0] # Average color for that block

    # Process all pixels in that block (blockSize x blockSize)
    0.upto(blockSize) do |x|
      next if (w + x) >= image.width # Check bounds!
      0.upto(blockSize) do |y|
        next if (h + y) >= image.height # Check bounds!
        # Get the RGB representation for that pixel
        color = ChunkyPNG::Color.to_truecolor_bytes(image[w + x, h + y])
        # Aggregate pixel value to the accumulative array
        sum[0] += color[0]
        sum[1] += color[1]
        sum[2] += color[2]
        # Another pixel processed for this block
        pixels += 1
      end
    end

    # Just calculate the average of the three components
    avg[0] = sum[0] / pixels
    avg[1] = sum[1] / pixels
    avg[2] = sum[2] / pixels

    # Update every pixel in the block with the same average color
    0.upto(blockSize) do |x|
      next if (w + x) >= image.width
      0.upto(blockSize) do |y|
        next if (h + y) >= image.height
        image[w + x, h + y] = ChunkyPNG::Color(avg[0], avg[1], avg[2])
      end
    end

    # Next row
    h += blockSize
  end
  # Next column
  w += blockSize
end

image.save('output.png')