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Pixelizing images with ChunkyPNG
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require 'chunky_png' | |
image = ChunkyPNG::Image.from_file('input.png') | |
width, height = image.width, image.height | |
image.resample_nearest_neighbor!(width/10, height/10) | |
image.resample_nearest_neighbor!(width, height) | |
image.save('output.png') |
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require 'chunky_png' | |
module ChunkyPNG | |
class Canvas | |
module BilinearResampling | |
def resample_bilinear!(new_width, new_height) | |
width_ratio = width.to_f / new_width.to_f | |
height_ratio = height.to_f / new_height.to_f | |
pixels = [] | |
1.upto(new_height) do |y| | |
1.upto(new_width) do |x| | |
pixels << get_bilinear_pixel((x-0.5)*width_ratio, (y-0.5)*height_ratio, width_ratio, height_ratio) | |
end | |
end | |
replace_canvas!(new_width, new_height, pixels) | |
end | |
private | |
def get_bilinear_pixel(x, y, sample_width, sample_height) | |
x = x - sample_width/2 | |
y = y - sample_height/2 | |
pixel_weights = [] | |
(y.floor..[(y+sample_height).ceil, height-1].min).each do |image_y| | |
weight_y = 1 | |
offset = y - image_y | |
weight_y = offset if offset > 0 | |
offset = image_y - (y + sample_height) | |
weight_y = offset if offset > 0 | |
(x.floor..[(x+sample_width).ceil, width-1].min).each do |image_x| | |
weight = weight_y | |
offset = x - image_x | |
weight = (weight_y ** 2 + offset ** 2) ** 0.5 if offset > 0 | |
offset = image_x - (x + sample_width) | |
weight = (weight_y ** 2 + offset ** 2) ** 0.5 if offset > 0 | |
pixel_weights << [get_pixel(image_x, image_y), weight] | |
end | |
end | |
total_weight = pixel_weights.inject(0){|acc,(_,w)| acc+w } | |
ChunkyPNG::Color.rgba( | |
(pixel_weights.inject(0){|acc,(p,w)| acc+ChunkyPNG::Color.r(p)*w }/total_weight).round, | |
(pixel_weights.inject(0){|acc,(p,w)| acc+ChunkyPNG::Color.g(p)*w }/total_weight).round, | |
(pixel_weights.inject(0){|acc,(p,w)| acc+ChunkyPNG::Color.b(p)*w }/total_weight).round, | |
(pixel_weights.inject(0){|acc,(p,w)| acc+ChunkyPNG::Color.a(p)*w }/total_weight).round | |
) | |
end | |
end | |
include BilinearResampling | |
end | |
end | |
image = ChunkyPNG::Image.from_file('input.png') | |
width, height = image.width, image.height | |
image.resample_bilinear!(width/10, height/10) | |
image.resample_nearest_neighbor!(width, height) | |
image.save('output.png') |
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