Module: ChunkyPNG::Canvas::StreamExporting

Defined in:
lib/papirus/chunky.rb

Instance Method Summary collapse

Instance Method Details

#inspect_bitstream(width, height) ⇒ Object

Creates a simple map of the image of ‘0’s and ‘1’s to STDERR this way you can view your image from the terminal set your terminals font very small, so the image will fit on your screen

Parameters:

  • width (integer) —

    The width of the image to inspect

  • height (integer) —

    The height of the image to inspect



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# File 'lib/papirus/chunky.rb', line 9

def inspect_bitstream(width, height)
    STDERR.puts to_1_bit_2_color_bw_image(width, height).each_slice(width).map{|row| row.each_slice(8).map{|pixels|pixels.map{|pixel| pixel < 128 ? '0' : '1'}.join}.join(' ')}.join("\n")
end

#to_1_bit_2_color_bw_image(width, height) ⇒ Object

Creates a rescaled image of whatever image is loaded image is rescaled to fit the width/height and is placed in the middle

Parameters:

  • width (integer) —

    width the image should be scaled to

  • height (integer) —

    height the image should be scaled to



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# File 'lib/papirus/chunky.rb', line 17

def to_1_bit_2_color_bw_image(width, height)
    resize(width, height).pixels.map{|pixel| ChunkyPNG::Color.grayscale_teint(pixel)}
end

#to_bit_stream(width, height, inverse = false, mingray = 128) ⇒ Object

As the EPD display needs 1-bit per pixel, which get written as a string to the fuse-fs display file and the ChunkyPNG library works with 4 bytes data per pixel (1 byte for R, G, B and transparancy) we need to load all the bits together in bytes, and packed those bytes into a string

Parameters:

  • width (integer) —

    width the image should be scaled to

  • height (integer) —

    height the image should be scaled to

  • inverse (boolean) (defaults to: false) —

    wether the image should be made negative

  • mingray (intergeri (0-255)) (defaults to: 128) —

    what grayscale value or higher is needed, to turn a bit on



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# File 'lib/papirus/chunky.rb', line 27

def to_bit_stream(width, height, inverse = false, mingray = 128)
    bytes = []
    #for each 8 pixels (the ChunkyPNG library keeps an array of all pixels used, containing ChunkyPNG::Color elements)
    to_1_bit_2_color_bw_image(width, height).each_slice(8).map do |pixels|
        #we create a byte with its bits set to 00000000
        byte = 0
        0.upto(7) do |bit|
            #and switch the bit to 1 (or 0 if not inverse) for each pixel if it was white
            #we have to check pixels[7-bit] as the order is right to left
            byte |= 1 << bit if (inverse && pixels[7-bit] > mingray) || (!inverse && pixels[7-bit] < mingray)
        end
        #and add it to the output byte stream
        bytes.push(byte)
    end
    #now we just need to pack all bytes into a file writable string
    bytes.pack('C*')
end