Class: Magick::Image

Inherits:
Object
  • Object
show all
Defined in:
lib/papirus/rmagick.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/rmagick.rb', line 9

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

#to_1_bit_2_color_bw_image(width, height) ⇒ Object

Creates a 1-bit 2-color 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/rmagick.rb', line 17

def to_1_bit_2_color_bw_image(width, height)
    # Resize to fit the screen
    resized = resize_to_fit(width, height)
    # Reduce the image to a limited number of colors for a "poster" effect, brings it donw to 4-bit 16 colors
    posterized = resized.posterize(2)
    #now, as the display expects a file with all pixels set, we need to extend the image to the display size
    #if it is smaller in either width or height or both
    if (posterize.columns != width or posterize.rows != height)
        # extent fill color
        posterized.background_color = "#FFFFFF"
        # calculate necessary translation to center image on background
        x = (posterized.columns - width) / 2
        y = (posterized.rows - height) / 2
        # now, 'extent' the image to the correct size with the image centered
        posterized = posterized.extent(width, height, x, y)
    end
    # Now, make grayscale with only 2 colors, b/w, brings it down to 1-bit 2 colors
    return posterized.quantize(2, Magick::GRAYColorspace)
end

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

As the EPD display needs 1-bit per pixel, which get written as a string to the fuse-fs display file 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



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# File 'lib/papirus/rmagick.rb', line 42

def to_bit_stream(width, height, inverse = false)
    bytes =[]
    # First, we convert whatever image we got to a 1-bit 2-color image,
    # then we traverse over the pixels in byte (8 bits) chucks to create our output bytes
    to_1_bit_2_color_bw_image(width, height).get_pixels(0, 0, 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].blue == 65535) || (!inverse && pixels[7-bit].blue == 0)
        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