Color > Merge Channels with non gray LUTs ?

[lechristophe]

Hi,

I just noticed that the "Merge Channels" command does not assigns the right
colors when starting from 8-bit images with an associated LUT different from
"grays". For example, using the spectrum LUT or the HiLo LUT for sources
images in the red and green channel will result in an addition of the two
images, keeping the original LUT rather than a Red-Green merge. This happens
for both vanilla ImageJ 1.44 and ImageJ 1.45e. Is this a bug or is this by
design ?

Christophe

[Gabriel Landini]

On Monday 18 Apr 2011 11:13:38 Christophe Leterrier
<[hidden email]> wrote:

> I just noticed that the "Merge Channels" command does not assigns the right
> colors when starting from 8-bit images with an associated LUT different
> from "grays". For example, using the spectrum LUT or the HiLo LUT for
> sources images in the red and green channel will result in an addition of
> the two images, keeping the original LUT rather than a Red-Green merge.
> This happens for both vanilla ImageJ 1.44 and ImageJ 1.45e. Is this a bug
> or is this by design ?

By design. According to the documentation:
"With IJ 1.44n and later, LUTs and display ranges are preserved if Create
Composite is chosen. "

Cheers
G

[lechristophe]

Thanks Gabriel, I didn't know that. However I did not use the "Create
Composite" option. Here are steps to reproduce the problem:

Open the blob image
Duplicate it
Put them both with the "HiLo" LUT
Stretch the contrast of the second one to make some red (saturated) pixels
appear
Color > Merge Channels
Choose green for the first blob, the other one in the "Gray" channel
"Create Composite" unchecked, "Keep Source" checked
You get a merge with red pixels and no green, meaning that both channels
have not been colored.

I think the problem is with the "Gray" channel as combinations of other
colors than gray (red, green, blue) are properly applied.

Christophe



On Mon, Apr 18, 2011 at 13:32, Gabriel Landini <[hidden email]> wrote:

> On Monday 18 Apr 2011 11:13:38 Christophe Leterrier
> <[hidden email]> wrote:
>
> > I just noticed that the "Merge Channels" command does not assigns the
> right
> > colors when starting from 8-bit images with an associated LUT different
> > from "grays". For example, using the spectrum LUT or the HiLo LUT for
> > sources images in the red and green channel will result in an addition of
> > the two images, keeping the original LUT rather than a Red-Green merge.
> > This happens for both vanilla ImageJ 1.44 and ImageJ 1.45e. Is this a bug
> > or is this by design ?
>
> By design. According to the documentation:
> "With IJ 1.44n and later, LUTs and display ranges are preserved if Create
> Composite is chosen. "
>
> Cheers
> G
>

[Gabriel Landini]

On Monday 18 Apr 2011 13:01:52 you wrote:

> Thanks Gabriel, I didn't know that. However I did not use the "Create
> Composite" option. Here are steps to reproduce the problem:
>
> Open the blob image
> Duplicate it
> Put them both with the "HiLo" LUT
> Stretch the contrast of the second one to make some red (saturated) pixels
> appear
> Color > Merge Channels
> Choose green for the first blob, the other one in the "Gray" channel
> "Create Composite" unchecked, "Keep Source" checked
> You get a merge with red pixels and no green, meaning that both channels
> have not been colored.
>
> I think the problem is with the "Gray" channel as combinations of other
> colors than gray (red, green, blue) are properly applied.

Hmm... I do not seem to be able to reproduce it.
I get a yellowish image... (attached)
ImageJ 1,45f9

Cheers

Gabriel

[lechristophe]

On Mon, Apr 18, 2011 at 15:09, Gabriel Landini <[hidden email]> wrote:

> On Monday 18 Apr 2011 13:01:52 you wrote:
> > Thanks Gabriel, I didn't know that. However I did not use the "Create
> > Composite" option. Here are steps to reproduce the problem:
> >
> > Open the blob image
> > Duplicate it
> > Put them both with the "HiLo" LUT
> > Stretch the contrast of the second one to make some red (saturated)
> pixels
> > appear
> > Color > Merge Channels
> > Choose green for the first blob, the other one in the "Gray" channel
> > "Create Composite" unchecked, "Keep Source" checked
> > You get a merge with red pixels and no green, meaning that both channels
> > have not been colored.
> >
> > I think the problem is with the "Gray" channel as combinations of other
> > colors than gray (red, green, blue) are properly applied.
>
> Hmm... I do not seem to be able to reproduce it.
> I get a yellowish image... (attached)
> ImageJ 1,45f9
>
>

That's strange... I get the redish overlay with both IJ 1.45e and 1.45f9

(attached).
ImageJ64 under Java 1.6.0_24 64bits, OSX 10.6.7




> Cheers
>
> Gabriel
>