Selection problem

I want to automatically select ALL greys in a layer.

Greys can be any RGB value, where R and G and B differ
no more than (say) 3.

For instance: I want to select both #101013 and #f0f1f0
(but not #101014 or #101410 or #0a1010).

How do I do this?

Thank you.

"Rhett" wrote in message

I want to automatically select ALL greys in a layer.

Greys can be any RGB value, where R and G and B differ
no more than (say) 3.

For instance: I want to select both #101013 and #f0f1f0
(but not #101014 or #101410 or #0a1010).

How do I do this?

Thank you.

Assuming you are using the magic wand to make the selection. . . .

In the Options Bar, check the "Add to Selection" box (second icon from the left, looks like 2 tiered pages)
Set the wand to the various shades of grey that you want to select and make the additional selections.
Vary the Tolerance value in the Options Bar to control how far the selection can deviate from your target value.

Remember, you can use the Quick Mask Tool to fine tune your selection, adding or subtracting areas in the selection by painting with a black (add) or white (subtract) brush over the selection.

Good Luck! . . . . patrick

Rhett wrote:

I want to automatically select ALL greys in a layer.

Greys can be any RGB value, where R and G and B differ
no more than (say) 3.

For instance: I want to select both #101013 and #f0f1f0
(but not #101014 or #101410 or #0a1010).

How do I do this?

Thank you.

Select>Color Range.

--
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

Assuming you are using the magic wand to make the selection. . . .
In the Options Bar, check the "Add to Selection" box (second icon from the left, looks like 2 tiered pages)
Set the wand to the various shades of grey that you want to select and

make

the additional selections.
Vary the Tolerance value in the Options Bar to control how far the

selection

can deviate from your target value.

Remember, you can use the Quick Mask Tool to fine tune your selection, adding or subtracting areas in the selection by painting with a black

(add)

or white (subtract) brush over the selection.

Good Luck! . . . . patrick

Thank you. The problem is that the Tolerance Value is absolute. This means I have to select all shades of grey with a tolerance of 3, and that is not practically
possible.

Here is one method (not complete) that I have just tried:

1. Duplicate layer
2. Remove Color in duplicated layer
3. Take Difference between duplicated layer and original, and Merge.
4. Make selection with Magic Wand and set Tolerance to 1 (not 3) on
the merged layer.

The problem here is that Remove Color makes an average. For instance: #c4c4c7 is transformed to #c5c5c5. The difference is now #010102. If tolerance is 1 than you only select greys with a difference less than 3 in the original.

"Rhett" wrote in message

Assuming you are using the magic wand to make the selection. . . .
In the Options Bar, check the "Add to Selection" box (second icon from the
left, looks like 2 tiered pages)
Set the wand to the various shades of grey that you want to select and

make

the additional selections.
Vary the Tolerance value in the Options Bar to control how far the

selection

can deviate from your target value.

Remember, you can use the Quick Mask Tool to fine tune your selection, adding or subtracting areas in the selection by painting with a black

(add)

or white (subtract) brush over the selection.

Good Luck! . . . . patrick

Thank you. The problem is that the Tolerance Value is absolute. This means I
have to select all shades of grey with a tolerance of 3, and that is not practically
possible.

Here is one method (not complete) that I have just tried:
1. Duplicate layer
2. Remove Color in duplicated layer
3. Take Difference between duplicated layer and original, and Merge.
4. Make selection with Magic Wand and set Tolerance to 1 (not 3) on
the merged layer.

The problem here is that Remove Color makes an average. For instance: #c4c4c7 is transformed to #c5c5c5. The difference is now #010102. If tolerance is 1 than you only select greys with a difference less than 3 in the original.

The tolerance value in the Options Bar can be set to anything from 1 to 255 (which would select everything!)
Again, the Quick Mask is ideal for this application.
Your work-around sounds clever, however.

.. . . . patrick

In article <AxVYe.1935$>,
"patrick" wrote:

In the Options Bar, check the "Add to Selection" box (second icon from the left, looks like 2 tiered pages)
Set the wand to the various shades of grey that you want to select and make the additional selections.
Vary the Tolerance value in the Options Bar to control how far the selection can deviate from your target value.

This is the long, tedious way to do it.

The quick way is to use the Color Range command in the Select menu. :)

--
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

"Rhett" wrote:

I want to automatically select ALL greys in a layer.

Greys can be any RGB value, where R and G and B differ
no more than (say) 3.

For instance: I want to select both #101013 and #f0f1f0
(but not #101014 or #101410 or #0a1010).

How do I do this?

Since I am exploring LAB at present ;) I suggest you try the following for selecting _all_ greys in an image:
Convert your image to LAB
Set the foreground swatch to 62L 0a 0b
Go to the a channel
Select color range, use fuzzines 5 or smaller
This selects all pixels which contain neither magenta nor green Save selection
Deselect
Go to the b channel
Select color range again.
Now you've selected all pixels which contain neither yellow nor blue Load the alpha channel you created earlier as a selection and set the mode to "intersect"
Now you've selected all pixels which contain no color information at all.
The fuzzines value limits the color tint which falls within your definition of "grey". If you minimize fuzziness you get shades of pure grey exclusively.
The value of 62L worked on both machines on which I tried it. I got it by reading out the value of the a and b channels in a greyscale image converted to LAB.

Peter