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From: nanren888 on 17 Jun 2010 05:20
I was trying larger colormaps.

len = 64;
im = [0:(len-1);(len-1):-1:0]; % ramp up & ramp down
figure(1);
image(im);
cm = hsv(len);
colormap(cm);
colorbar();
figure(2); plot(cm); colormap(cm);

Pretty much as I expect. A couple of ramps with a colorbar. figure(2) shows the correct colormap.

len = 164;im = [0:(len-1);(len-1):-1:0];figure(1);image(im);cm = hsv(len);colormap(cm);colorbar();figure(2);plot(cm);colormap(cm);

Same

len = 264;im = [0:(len-1);(len-1):-1:0];figure(1);image(im);cm = hsv(len);colormap(cm);colorbar();figure(2);plot(cm);colormap(cm);

Now a black bar appears at the top.

len = 1264; ...

The whole graph goes black.
figure(2) still shows correct colormap values, but not the image nor the colorbar.

Mapping is default 'direct'. Image content is double.

Seems that something about 'direct' access of colormaps in images wraps at 255.
Anyone explain it to me?
Thanks, in advance.
From: us on 17 Jun 2010 05:46
"nanren888 " <nanren888.remove.this(a)hotmail.com> wrote in message <hvcpcm$7db$1(a)fred.mathworks.com>...
> I was trying larger colormaps.
>
> len = 64;
> im = [0:(len-1);(len-1):-1:0]; % ramp up & ramp down
> figure(1);
> image(im);
> cm = hsv(len);
> colormap(cm);
> colorbar();
> figure(2); plot(cm); colormap(cm);
>
> Pretty much as I expect. A couple of ramps with a colorbar. figure(2) shows the correct colormap.
>
> len = 164;im = [0:(len-1);(len-1):-1:0];figure(1);image(im);cm = hsv(len);colormap(cm);colorbar();figure(2);plot(cm);colormap(cm);
>
> Same
>
> len = 264;im = [0:(len-1);(len-1):-1:0];figure(1);image(im);cm = hsv(len);colormap(cm);colorbar();figure(2);plot(cm);colormap(cm);
>
> Now a black bar appears at the top.
>
> len = 1264; ...
>
> The whole graph goes black.
> figure(2) still shows correct colormap values, but not the image nor the colorbar.
>
> Mapping is default 'direct'. Image content is double.
>
> Seems that something about 'direct' access of colormaps in images wraps at 255.
> Anyone explain it to me?
> Thanks, in advance.

the problem is hw related...

one of the solutions

figure;
colormap(hsv(1024));
colorbar;
disp('all red - cont with any key');
pause;
set(gcf,'renderer','opengl');
% full cmap...

us
From: nanren888 on 17 Jun 2010 05:56
us, thanks for the fix. Works a treat.

Sorry, exactly what is broken?
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