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PyPNG for drawing a simple filled box

I am trying to draw a simple RGBA square of 256x256 pixels using the python png module.

I would like to use the png.Writer function, and I guess I would have to use it using the write () method. However, I’m out of luck! I do not believe in my current code, so I am ready to accept offers from scratch

I prefer not to use PIL if possible.

Any suggestions?

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I think the format may affect you, it seems that it pnghas three formats ...

>>> help(png)
    Boxed row flat pixel::

     list([R,G,B, R,G,B, R,G,B],
       [R,G,B, R,G,B, R,G,B])

    Flat row flat pixel::    

      [R,G,B, R,G,B, R,G,B,
       R,G,B, R,G,B, R,G,B]

    Boxed row boxed pixel::

      list([ (R,G,B), (R,G,B), (R,G,B) ],
           [ (R,G,B), (R,G,B), (R,G,B) ])

Alpha is added at the end of each RGB sequence.

 write(self, outfile, rows)
 |      Write a PNG image to the output file.  `rows` should be
 |      an iterable that yields each row in boxed row flat pixel format.
 |      The rows should be the rows of the original image, so there
 |      should be ``self.height`` rows of ``self.width * self.planes`` values.
 |      If `interlace` is specified (when creating the instance), then
 |      an interlaced PNG file will be written.  Supply the rows in the
 |      normal image order; the interlacing is carried out internally.

pay attention to each row in boxed row flat pixel format.

Here is a quick example that draws a white square.

>>> rows = [[255 for element in xrange(4) for number_of_pixles in xrange(256)] for number_of_rows in xrange(256)]
>>> import numpy # Using numpy is much faster
>>> rows = numpy.zeros((256, 256 * 4), dtype = 'int')
>>> rows[:] = 255
>>> png_writer = png.Writer(width = 256, height = 256, alpha = 'RGBA')
>>> png_writer.write(open('white_panel.png', 'wb'), rows)

, Writer 2 , , , .

     |  write_array(self, outfile, pixels)
     |      Write an array in flat row flat pixel format as a PNG file on
     |      the output file.  See also :meth:`write` method.
     |  
     |  write_packed(self, outfile, rows)
     |      Write PNG file to `outfile`.  The pixel data comes from `rows`
     |      which should be in boxed row packed format.  Each row should be
     |      a sequence of packed bytes.

numpy , .

.

, RGB , , (255, 0, 0, 255).

import png
import numpy
rows = numpy.zeros((256, 256, 4), dtype = 'int') # eassier format to deal with each individual pixel
rows[:, :] = [255, 0, 0, 255] # Setting the color red for each pixel
rows[10:40, 10:40] = [0, 255, 255, 255] #  filled squared starting at (10,10) to (40,40)
locs = numpy.indices(rows.shape[0:2])
rows[(locs[0] - 80)**2 + (locs[1] - 80)**2 <= 20**2] = [255, 255, 0, 255] # yellow filled circle, with center at (80, 80) and radius 20
png_writer = png.Writer(width = 256, height = 256, alpha = 'RGBA') # create writer
png_writer.write(open('colors_panel.png', 'wb'), rows.reshape(rows.shape[0], rows.shape[1]*rows.shape[2])) # we have to reshape or flatten the most inner arrays so write can properly understand the format
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