[Numpy-discussion] Help with bit arrays

Henrique Almeida hdante.lnls at gmail.com
Fri Apr 29 12:31:26 EDT 2016


 Paul, yes, imread() worked for reading the black and white TIFF. The
situation improved, but now, there seems to be some problem with the
color map. Example code:

#!/usr/bin/env python3
import numpy
from matplotlib import pyplot, cm

img = pyplot.imread('oi-00.tiff')
pyplot.imshow(img)
pyplot.colorbar()
pyplot.show()

 The code can open both 1-bit and 8-bit images, but only with 8 bits
the image is shown with the colormap colors. The 1 bit image is shown
as black and white.

 The questions:
 1) Should Image.open() behave like pyplot.imread() ? Is this a bug in PIL ?
 2) Why isn't the colormap working with black and white images ?

2016-04-29 13:06 GMT-03:00 Paul Hobson <pmhobson at gmail.com>:
> Does using pyplot.imgread work?
>
> On Fri, Apr 29, 2016 at 8:27 AM, Henrique Almeida <hdante.lnls at gmail.com>
> wrote:
>>
>>  Any help with this problem ?
>>
>> 2016-04-27 11:35 GMT-03:00 Henrique Almeida <hdante.lnls at gmail.com>:
>> >  Hello, what's the current status on numpy for loading bit-arrays ?
>> >
>> > I'm currently unable to correctly load black and white (1-bit) TIFF
>> > images. Code example follows:
>> >
>> > from PIL import Image
>> > import numpy
>> > from matplotlib import pyplot
>> >
>> > img = Image.open('oi-00.tiff')
>> > a = numpy.array(img)
>> >
>> > ^ does not work for 1-bit TIFF images
>> >
>> > PIL source shows that it incorrectly uses typestr == '|b1'. I tried to
>> > change this to '|t1', but I get :
>> >
>> > TypeError: data type "|t1" not understood
>> >
>> > My goal is to make the above code to work for black and white TIFF
>> > images the same way it works for grayscale images. Any help ?
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>
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