Hi William,
I looked at the data you sent me. The problem is likely overexposed and
that basically means very white value have band 1 to 3 set at
255,255,255. I tried three solutions.
The first is to make all the white pixels null pixel. Then adding a
Google Satellite layer under. The nodata pixels are transparent. That
solution does not work basically because of pixel misregistration
between both layers. It looks bad. See 2layer_solution in the project I
sent you.
The second option is to interpolate the nodata values (the white) using
t.fill.stats found in the Processing toolbox, and then recombining the
bands (look at the Interpolated_band123 layer) That could work but
generally, pixel tend to become much darker. This should not be the case
because we are dealing with highlights. Also, you have some highlights
that are not 255,255,255 but very close. They now stick out. Maybe a
better interpolation can be found. I did not play with this much.
The best solution is the simplest. Use the green local stretch icon in
the raster toolbar (you may need to activate it). Under layer > layer
properties > Symbology set render type to multiband color. Red: min =
32, max =207, Green: min = 26, max = 179, and Blue: Min = 33, max 152
give good results. But basically zoom in and click the icon.
This way, you will not notice the overexposure and the colors will be
nicer.
Cheers!
Nicolas
On 2020-05-24 12:01 a.m., William Reynolds wrote:
I have a raster image I would like to assign a value to the 3 RGB
bands that are equal to 255. I have several hundred raster images
where the image is overexposed (white) and band1=255, band2=255 and
band3=255.
Is there a way to run a script that would assign a new value to each
of the three bands if the band1, band2 and band3 values = 255?
Bill
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