How to read JPG2000 with Python?

Question

I have read several JP2 (JPEG200) images with matplotlib and got numpy arrays with big numbers, exceeding 40000.

Reading code:

img_blue =mpimg.imread('B02.jp2')
img_green =mpimg.imread('B03.jp2')
img_red =mpimg.imread('B04.jp2')

Data is:

[[12290 12694 13034 ...,  1968  2078  2118]
 [12174 12374 12696 ...,  1998  2068  2134]
 [12422 12522 12512 ...,  1990  1972  1990]
 ..., 
 [ 4268  4276  4064 ...,     0     0     0]
 [ 4174  4114  3938 ...,     0     0     0]
 [ 3954  4036  3906 ...,

What does this data mean?

Does it mean JP2 can contain larger dynamic range? How can I convert it to normal image? Just normalize? What is denominator?

Example of file is here: http://sentinel-s2-l1c.s3.amazonaws.com/tiles/37/U/DB/2017/5/10/0/B02.jp2

user_10993926 · Answer

I just divide 22.5 to B02,B03,B04 and combine it.

saw this page https://knowledge.safe.com/articles/43742/making-rgb-images-with-sentinel-data.html

my code is

b_r = im_b_04/22.5;
b_g = im_b_03/22.5;
b_b = im_b_02/22.5;

RGB_gt = numpy.zeros([len(b_r), len(b_r[0]), 3], np.uint8)
RGB_gt[:, :, 0] = b_r;
RGB_gt[:, :, 1] = b_g;
RGB_gt[:, :, 2] = b_b;

it works.

user_13358139 · Answer

import rasterio

ds = rasterio.open(path_to_jp2_image)
ds.read(1)

see: can't open jp2 (from sentinel) with python rasterio,gdal

How to read JPG2000 with Python?

3 Answers