B&W image to user defined colour gradient?

[SteveL]

I have a bit of a mind block that I was wondering if anyone can help me with.

Say I have a grayscale image, and I wanted to turn it into a colour image that is mapping the black->white gradient to a specific colour palette, how would I go about doing this in PSCS? (And I dont mean I want a grey scale turned into a blue scale, I want different RGB colours at different gray intensities).

Any ideas?

[MartinB]

Not sure I quite get it Steve. Is this for something like a light pollution gradient filter that you want to make the colour of the LP/it's inverse?

[trevboyd]

Martin, I assumed it was to convert a grayscale image to something resembling a temperature map on the TV weather.

e.g.

Black - cold - dark blue

Mid gray - medium - yellow/green

White - holt - red

with all the variations in between.

No idea how you'd do it though! Be very interested in any solution anyone comes up with, as it sounds really useful...

Trev

[steppenwolf]

Steve,

I can tell you how to do it in two colours (NOT Duotone!) if that helps?

You can use Index Colour to transform a greyscale image into a pseudo-colour image by creating a colour table based on the image and then changing the colours in the table.

1. Convert the greyscale image to 'indexed colour' by choosing:-

Image > Mode > Indexed Colour.

2. Access the image's colour table by choosing:-

Image > Mode > Colour Table.

Once the dialogue box appears, click in the colour swatch at the upper left-hand corner of the table and drag to the swatch at the lower-right hand corner. As soon as you release the mouse button, the Colour Picker will appear allowing you to pick the first of the colours for your two-colour blend.

3. Select a colour and click 'OK'. The Colour Picker will appear again immediately.

4. Select your second colour and click 'OK'. Your colour table now contains swatches of the various blend steps. If you're happy with the blend colour scheme, click 'OK' and the new colour scheme will be applied to the image instantly.

5. To get a multi-coloured image, go back to the colour table:-

Image > Mode > Colour Table.

and select 'Spectrum' and watch it come alive!!

This is an Ha image of the North America Nebula:-

Hope that helps!

[SteveL]

Trev is spot on, and I think I found a solution using Gradient Maps, but need to play with it some more

[steppenwolf]

Is what I have demonstrated not what you wanted?

[CELESCOPE]

I like that Steve looks pretty ehhehe

[trevboyd]

Steve's example looks like what I was describing (or at least what I intended to describe....)

Trev

[SteveL]

Is what I have demonstrated not what you wanted?

It could well be, I`ll have a play with both options when I get some time.