from_rgb_stream : calculation of width and height about chunky_png HOT 6 CLOSED

After parsing the RGB stream, the resulting Canvas has #width and #height that you can call

from chunky_png.

Thanks wvanberge but i wasn't specific enough. Here is the code :

require('chunky_png')
include(ChunkyPNG)

# Constants

RGB_SIZE = 6

binary = File.open('./data', 'rb')
hexStream = ""
binary.each_char() do |char|
    hexStream += char.unpack('H*').join()
end
binary.close()

rgbStream = hexStream.scan(/.{#{RGB_SIZE}}/)

if (rgbStream.last().size() === RGB_SIZE)

    # how to calculate the correct width and height ?
    ChunkyPNG::Canvas.from_rgb_stream(74, 74, [rgbStream.join()].pack('H*')).save('./test.png')

end

from chunky_png.

You can't calculate those: an RGB strean is just a stream of pixels, so there's no way to know whether a stream of 4 pixels is a 1x4 image or a 2x2. This is why you have to supply these arguments.

from chunky_png.

If we know the number of pixels in an image of 1x1 it can not help me, according to the DPI used by 'ChunkyPNG::Canvas' ?

from chunky_png.

from_rgb_stream basically is: "please construct a canvas of this size, and use this pixeldata for it."

If you know the image is 1x1, you can use 1, 1 as first two arguments to from_rgb_stream. The RGB stream for the third argument should then be 3 bytes long.

from chunky_png.

Thank you very much, "chunky_png" is an elegant solution.

from chunky_png.