Setting transparent backgrounds

GuanYin

Hi,

I was hoping you super photo gurus could help me out here.

I have three tracer images taken off a very PC unfriendly piece of medical equipment. So unfriendly that my only means of obtaining them is through a printout.

There is no option to set line thickness so it is a very faint line on white paper.

I've scanned these images at around 300dpi and I now want to set the background as transparent so I can overlap them, changing the line colors would be a great bonus.

Unfortunately, the lines are so feint that when I try the simple options on photoshop, the image is terrible. I can't seem to find a way to thicken the lines or even change color.

Can anyone help or offer suggestions or a quick guide (I'm a computer ditz )

Thanks

L

Gordon

Is it just line drawings that you have? You can try a quick workaround by messing with the layer blends. I am presuming that the backgrounds are white and the lines are light black/grey?

Put each image on a new layer.
Click on the top layer and where it says "Normal" (a drop down box - the layer blend I think it's called) click "Darken".
See if that helps, then do it to the other layers and it should make the white transparent and the dark should pull through.

If that fails then try other blending types. If that fails then you could vectorise it. Is it a complicated image? Can you post one up?

GuanYin

Unfortunately I'd be breaking several laws if if posted one up as they have patient details on them

Thanks ever so much for your answer though, I'll try it out now and report back

Gordon

Ah! What's a tracer image then, is it like an X-Ray or a complicated medical image?

GuanYin

The image is just a trace, much like an ECG. its a feint black line peaking and troughing.

GuanYin

Ok, the darken thing seems to have worked, I'm still left with lines so feint I can barely see them. Anyway way of auto thickening the lines?

Gordon

I see, like this?


You can also try going to Image>Adjustments>Brightness and Contrast to mess around with the clarity of the lines. And then also try Image>Adjustments>Levels and mess around with the sliders of the output of the dark and light.

It may not thicken the lines but at least make them a great deal darker.

If you could crop a section of the image and post it up I or someone else could tell you a more specific action to do.

GuanYin

its like that image but without the grid and with a thin black line instead of a red one.

I'll paste up a piece of it now

GuanYin

Ok, here is a peak of the trace

Gordon

Yeah that's pretty bad. I tried a few things and actually the nicest solution seems to be Image>Adjustments>Auto Levels. That should make it workable.

Gordon

If you want thicker lines you could try this:

Filter>Sharpen>Unsharp Mask

Then put the maximum amount, the maximum radius and the minimum threshold and that will give you a (dirty) thicker line.

GuanYin

Ohh yes, thank you. That will work.

I think they deliberately made this machine so images couldn't be taken from it.

COMRIB and that kinda patient rights nonsense

Thanks so much again

Gordon

Cool.

nadasky08

Can't you just use a pen/lasso+stroke tool to trace over the lines?

Richard O' Shea

goto the levels adjustment and bring levels up so the blacks become more defined. use the magic wand tool to select the outline, this will allow to delete the backround and keep just the black lines with an alpha backround instead.