Change Coloured Image to B/W Without Losing Details.

[moil60]

Hello I've scanned an image which is black on a purple piece of paper. I would like to print the black details on a white piece of paper.
So in other words i would like to get rid of the purple colour. However i tried doing this using the contrast and brightness tools (which works) but when i print it I keep losing the detail in the writing. When i print it out its at a very low resolution. How can i overcome this to it will print at the same resolution as the scanned image?

any help would be appreciated. cheers.

 

[dv8_fx]

There are different ways to do this.

One is to redo everything in Microsoft Word.... a lot of work.


In PS will take a bit of work... here's one way....


Click out all other channels leaving Blue visible in the channels palette .
In Hue and Saturation, set saturation at +100 and Lightness at -10. Click OK.



You may need to tweak Brightness and Contrast to get the whitest whites and blackest black.
CTRL+click the blue channel icon to select the white in the layer.. Then Inverse selection to select black.
Create a new layer. Fill selection with black. Repeat fill to get a darker shade. Deselect.
Fill background layer white. But if you need the original BG image layer, do the fill on a new layer.

If the other RGB channels aren't activated by this time, activate them. (Tho not necessary). Save as PSD.

Flatten image.... there's you're B&W document. Save as JPG.

Depending on outcome on entire document, you may need to use sharpen filters on the image a bit.


Hoping the scan didn't pick up show through elements/text from the reverse side of the scanned page...... it's gonna be hell to delete/clean them out... lol

 

[Tom Mann]

Another approach is to put a black and white adjustment layer above the image layer, and push the magenta slider to the right until the Background becomes white.

 

[dv8_fx]

Like I said... many ways. Tom's suggestion would be the most obvious, quick way.

 

[Tom Mann]

Yup, as dv8 noted, as always, there usually are many ways to accomplish something in Photoshop. Assuming you have a good knowledge of PS, the choice between them is usually influenced by factors such as quality of the result, time and complexity of each of the competing approaches, suitability of the final format, etc.

In the case of the example you posted, the noise / grain / texture can cause problems, especially to fast, simple methods like the one I suggested in my last post. Of course, you can add a few more processing steps to help matters out, but these take time and may require extra software.

For example (see layer stack and result posted below), I processed your image with Topaz "Clean" before using the B&W adjustment layer on it. Then, to get a nice, high contrast image, I followed this with a "curves" adjustment layer. Each of these extra steps take time to optimize. Maybe it's worth it, maybe not. Maybe a slightly softer version is adequate, or even more suitable for your application.







A completely different approach that you may want to consider is to simply feed your image into an OCR program. OCR programs are designed to deal with exactly the problems present in your example image, and give a result in the form of a text file that could be used in many ways, not the least of which is that it's essentially infinitely sharp and can be magnified to any size. This approach is a more automated version of the "Typing it over" possibility mentioned by dv8. Again, you have to look at this approach in the context of the overall goals and constraints on the project (eg, are you just doing a few words, or pages and pages of text).

HTH,

Tom

 

[Tom Mann]

PS - BTW, I do almost no OCR, so the OCR program that I used, ABBYY Free Reader, was a free one that I have had around for at least 5 years. I'm sure much more competent ones are available these days.