On Tue, Apr 11, 2006 at 04:57:08PM -0400, Haines Brown wrote:

I have a simple line drawing that is in shades of light grey against a white ground. My aim is to increase the grey scale range from 000 199 to 000 to 255.

Grokking the Gimp suggests I should use the Threshold Tool, but this produces unsatisfactory results. By moving the sliders I can darken the light grey to black, but what I'm left with is just what had been the original very darkest greys, and the lighter greys disappear.

Am I just being clumbsy, or is there a better approach?

try using the levels tool.

carol

My aim is to increase the grey scale range from 000 199 to 000 to 255.

More specifically use levels and slide the left hand and right hand sliders in towards where your histogram starts.

hi,

i found any downsampling ( scale image to a smaller size ) will definitely blur the image ( scaned from film ) to an undesired degree. is there any suggestion around that? using a unsharp-mask after every downsampling ?

thanks.

Hi Haines,

Haines Brown wrote:

Am I just being clumbsy, or is there a better approach?

try using the levels tool.

Thanks, Carol, I did as you suggested. It works, although the result was unsatisfactory because the original image distribution of greys was uneven, and so the result was spotty (gaps in lines, artifacts, etc.). I guess I try to draw a new image myself.

You could try playing with the middle (gamma) slider to get better results, or use the curves tool rather than the levels tool - it gives you a bit more control.

Please excuse the appended question, but is there a way I could use the original as a kind of template to produce a hard line clean version in black? I could then blur it a bit for a nice result.

You could create a new layer on top of your original, and set the layer mode in "overlay" - that way you will see your original drawing underneath, which you can draw on afterwards.

Cheers, Dave.

On Wed, Apr 12, 2006 at 11:41:27AM -0400, Haines Brown wrote:

On Tue, Apr 11, 2006 at 04:57:08PM -0400, Haines Brown wrote:

I have a simple line drawing that is in shades of light grey against a white ground. My aim is to increase the grey scale range from 000 199 to 000 to 255.
...

Am I just being clumbsy, or is there a better approach?

try using the levels tool.

Thanks, Carol, I did as you suggested. It works, although the result was unsatisfactory because the original image distribution of greys was uneven, and so the result was spotty (gaps in lines, artifacts, etc.). I guess I try to draw a new image myself.

Please excuse the appended question, but is there a way I could use the original as a kind of template to produce a hard line clean version in black? I could then blur it a bit for a nice result.

use the original to make a mask.

it has been a long while since i worked with scans, but iirc, i used the levels to get rid of the noise. after that, the threshold tool. blurring the black and white result of the thresholded image will add the grays back nicely. invert this layer.

then stack first a solid background color and then over that, whatever color you want your lines to be (black looks like what you want) then use the mask you made on this layer.

carol