[argyllcms] Re: ArgyllCMS: shadow details and blue color issues. What I'm doing incorrectly?

  • From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 25 Oct 2012 08:39:37 +0400

Thu, 25 Oct 2012 01:58:39 +0200 "Xavi" wrote:

>I also have analized this case. I have compared the original 
tiff file generated by printtarg versus the resized, with Ps, tiff file nad the 
values of every patch is exactly the same.OK. This is not a source the problem.

>On another email you commented " I'm using ImageMagic "convert" utility to 
>crop and resize Argyll targets 
into desirable format."
I see that your patches, after this converssion, haven't a regular color. For 
exampl, if I analize the yellow color patch with Ps, the information of each 
pixel varies. A pixel has a Lab 243,222,88 and the pixel that limites has a 
value 242.221,87 [Lab]. This not occurs when resizing with Ps. All the pixels, 
of a same color patch, have the same Lab value.I've didn't use ImageMagic for 
preparing Test4.tif. This pixel difference is due to enabled dithering in 

>...I used a resized TIFF file, created without the -D (ÂDither 8 bit TIFF 
>values down from 16 
you think that's important to use the -D option when create the TIFF 
file?The spatial dithering allows to print arbitrary RGB values, not only 
INTEGER 0..255, for example, You had to round RGB values from xicclu -fb or 
-fif to closest integer. With dithering enabled, the dithering algorithm will 
mix-up the pixels of different but closest values to obtain desirable 
intermediate value with higher tolerance. You can use 16-bit raster images, but 
when printing they will be re-quantized down to 8 bit with dithering by 
Photoshop or another SW. I'm enabling the dithering almost always if I use 
8-bit images. I want not to loss intermediate device values.

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