What kind of array is "img"? What is its dtype and shape?

plt.imshow() will use the default colormap for matplotlib if the given array is just 2D. But if it is 3D (a 2D array of RGB[A] channels), then it will forego the colormap and utilize that for the colors. It knows nothing of the colormap contained in the TIFF.

Ben Root


On Fri, Apr 29, 2016 at 12:31 PM, Henrique Almeida <hdante.lnls@gmail.com> wrote:
 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@gmail.com>:
> Does using pyplot.imgread work?
>
> On Fri, Apr 29, 2016 at 8:27 AM, Henrique Almeida <hdante.lnls@gmail.com>
> wrote:
>>
>>  Any help with this problem ?
>>
>> 2016-04-27 11:35 GMT-03:00 Henrique Almeida <hdante.lnls@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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