Understanding and Converting Ruby's ChunkyPNG to Javascript Equivalent

Question

I am converting some RUBY code into Javascript. This RUBY code uses ChunkyPNG Ruby Library.

Here is the Ruby Code:

def self.from_png(file)
  image = ChunkyPNG::Image.from_file(file)
  mask = Mask.new(image.height, image.width)

  mask.rows.times do |row|
    mask.columns.times do |col|
      if image[col, row] == ChunkyPNG::Color::BLACK
        mask[row, col] = false
      else
        mask[row, col] = true
      end
    end
  end

  mask
end

How to convert the above code to Javascript? The 2 lines I am facing challenges with converting are:

image = ChunkyPNG::Image.from_file(file)

and

if image[col, row] == ChunkyPNG::Color::BLACK

What Javascript PNG library can I use to do the same?

What does

image[col, row]

refer to? is it RG in RGB?? or what is it? Understanding this can help me find the equivalent Javascript method in Javascript PNG Libraries ...

Must be color, probably number by comparision - image[col, row] == ChunkyPNG::Color::BLACK looks like black background(?) is used as transparent background around image ? It is number - here https://github.com/wvanbergen/chunky_png/blob/master/lib/chunky_png/color.rb — Jan, Aug 01 '19 at 09:14

score 1 · Accepted Answer · answered Aug 01 '19 at 09:25

image[col, row] refers to specific pixel of the image at position (col, row). Image can be described as 2D array of colors - in this case, color is an instance of ChunkyPNG::Color or just a number. In your code sample all black pixels marked as false in the mask, all non-black marked as true.

Understanding and Converting Ruby's ChunkyPNG to Javascript Equivalent

1 Answers1