What Is Best Way To Make Black and White Print?

[abrogard]

I have a picture of a sheet of music which came from a colour photograph .jpg and then was converted to grayscale in Gimp.

That hasn't make it black and white but instead gives me an overall grey cast on my HP black and white printer.

I tried setting it for indexed colour on black and white and that was terrible.

I have a whole heap of these to do and it would be good if I could find a quick simple way.

A few years ago I used to use Paintshop pro and if I remember right I had a kinda two keystroke fix for this - I think I just set it for a low color depth or something.

There's be something in Gimp I imagine?

I'll attach the particular one I mean today.

[Ofnuts]

You can just use the Brightness/Contrast tool and add contrast, or use Colors>Auto>Stretch contrast. In both cases one problem is the uneven lighting across the page.

A better technique is to:

• Use Filters>Enhance>Wavelet decompose, decompose to the maximum levels
  
• Bucket-fill the "Residual" layer with white (this will even out the background)
  
• Layer>New from visible to get a new layer (and move it to the top)
  
• Apply Color>Levels to that layer: in the input section move the leftmost handle to the beginning of the histogram, and perhaps move the middle handle to increase contrast.
  

   

[david]

This is something I do regularly, usually from scanned images.
I find the best way of getting usable results is with Colours/ Curves. Pull the top right corner and bottom left corner towards the middle. You will quickly find the position which gives the best compromise.

david.

   

[abrogard]

Thanks for that.  I got somewhere with the  color curves thing but I did something wrong with the wavelet decompose and just finished up with a mess.


       

[Kevin]

I find if I use the High-Pass filter first, putting the contrast to max and increasing the Std-Dev it makes the "blacks" and "white" more uniform
   

Then using the Levels to make the blacks properly black and the whites, white:
   

[abrogard]

Well that last technique seemed the best. I got a clean looking black and white image in the end. I opted for adjusting levels by curves and I pulled a 'bump' out in the middle of the curve and it seemed to magically get rid of the darkness of the uneven lighting at the top right.

So that was beaut.

But when I printed it I got the worst image yet. Did I not do something I should have done to preserve those alterations?

All of this has brought back vague memories of doing this years ago with some prog or other and what I had to do was set a 'cut off' point where anything t his side of it was seen as black by the editor 'black' and anything the other side was seen as 'white'.

Is that perhaps what these levels are doing or would be doing if i used them correctly?

[Ofnuts]

With the wavelet decompose, the visible image before you bucket-fill with white looks exactly like you initial image, and once you bucket fill you get the same image but with a white background and a lower contrast. Your problem is somewhere at the bottom of your layer stack, it looks like you applied some threshol/contrast tool to on eo the bottom layers.

[Krikor]

I tried to follow the instructions in posts #2, #3 and #5, and the best results I got were:
1- #2
2- #5
3- #3
   

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I believe that the tips from rich2005 and Ofnuts in the posts below would also give excellent results!

#2 - https://www.gimp-forum.net/Thread-removi...0#pid15370

#3 - https://www.gimp-forum.net/Thread-removi...5#pid15375