This may seem like a duh! question with an obvious answer, but I'd like to confirm:
As stated in a previous post, my line drawings for my print book use solid black lines, lines in two shades of gray, and a few gray gradients (i.e. no color at all). It would seem to me that these are already in grayscale by definition ( a requirement for b+w print books), and therefore there is no need for me to go through all of them and convert each one to grayscale. In other words, grayscale is only appropriate and necessary for converting color images to b+w.
The possible unknown for me is if there is some sort of useful metadata applied to a graphic when applying grayscale that is necessary even if it was originally created in black and gray.
I've poked around in Inkscape and the only place to apply grayscale to an image that I can find is via Extensions > Color > Grayscale, seemingly confirming that grayscale can only be applied to color images/graphics.
Thanks Ken, interesting info. The second link seems to me a huge amount of work bringing in another program (GIMP) and going through a number of steps for my purposes. Since my original post I have done some subsequent research which made me more informed and aware, and reminded me that simple things are often more - sometimes much more - complex than they first appear. With that in mind, a few more comments/questions:
Without thinking much about it, when I was creating my graphics I used RGB color space to create the shades of gray that I wanted. Grays are made up of equal levels of all three color spaces as you all know, so that made me wonder if grayscaling objects would somehow change that. The only thing I could think of that might happen is that the objects would change to solid black (0,0,0 on the RGB scale) with the alpha channel reduced by a certain percentage depending on the lightness/darkness of the shade of gray (which would actually create a transparency it seems to me - a no-no for some book printing vendors). This did not happen, however; the RGB numbers stayed the same and the alpha channel remained at 100% (see below for the numbers).
I now understand that RGB is used for computer graphics while CMYK is used for print graphics. On the RGB scale, I entered 120 for R, G, and B to create a darker gray that I wanted, and 160 each for a lighter shade. I may have also used 80 each a few times.
A moment ago I did a test: in Inkscape, I created a black rectangle, a lighter gray circle (160 RGB each), and a darker gray arc (120 RGB each). I then selected the gray objects and clicked on Extensions>Color>Grayscale. Nothing changed in the RGB panel; the entries were still 120-120-120 or 160-160-160.
So I switched to the CMYK color space panel, selected the lighter gray circle (160 each on the RGB scale), and this showed as cyan=0, magenta=0, yellow=0, and black at 37%. Aside: on other online conversations which discussed K references I did not know what that meant; now I know that it refers to the K (black) in CMYK. No wonder I was confused as to what "K" referred to since I was using RGB which has no K obviously. I assume that the K space is not actually an alpha channel as is the corresponding A channel in RGB even though they both seem to affect transparency.
Another test I did was to create a black circle while in CMYK (0,0,0,100%), and shift the K channel to 37%. No surprise, when switching to RGB it showed 161, 161, 161, with the alpha channel at 100%. What I don't get is that CMYK, RGB, and other color spaces are using different languages/terminology for describing and depicting the very same thing. So if I create an image using RGB, it is automatically formatted accordingly in CMYK as well as all other color spaces. I cannot create a graphic that is ONLY in RGB, or CMYK - so what difference does it make? Perhaps it has to do with the rendering/printing process rather than the creation process, i.e. printers will use the CMYK framework while computer rendering will use the RGB framework.
So if I understand things correctly, for my print book project there is no need to convert my 'RGB' graphics to CMYK to ensure that they are grayscaled - they already are even though I created them using the RGB framework.
Beginners' Questions Grayscale images question
Inkscape.org
This may seem like a duh! question with an obvious answer, but I'd like to confirm:
As stated in a previous post, my line drawings for my print book use solid black lines, lines in two shades of gray, and a few gray gradients (i.e. no color at all). It would seem to me that these are already in grayscale by definition ( a requirement for b+w print books), and therefore there is no need for me to go through all of them and convert each one to grayscale. In other words, grayscale is only appropriate and necessary for converting color images to b+w.
The possible unknown for me is if there is some sort of useful metadata applied to a graphic when applying grayscale that is necessary even if it was originally created in black and gray.
I've poked around in Inkscape and the only place to apply grayscale to an image that I can find is via Extensions > Color > Grayscale, seemingly confirming that grayscale can only be applied to color images/graphics.
Comments?
Hi. I never really thought much about this or investigated myself. But I did find the topic below. Hope this helps you.
https://graphicdesign.stackexchange.com/questions/134462/how-can-i-apply-a-filter-permanently-without-rasterizing
And the link below which gets into using Gimp and other aspects in Inkscape.
https://inkscape.org/forums/questions/converting-various-separated-colors-in-an-image-to-1-bit/
Thanks Ken, interesting info. The second link seems to me a huge amount of work bringing in another program (GIMP) and going through a number of steps for my purposes. Since my original post I have done some subsequent research which made me more informed and aware, and reminded me that simple things are often more - sometimes much more - complex than they first appear. With that in mind, a few more comments/questions:
Without thinking much about it, when I was creating my graphics I used RGB color space to create the shades of gray that I wanted. Grays are made up of equal levels of all three color spaces as you all know, so that made me wonder if grayscaling objects would somehow change that. The only thing I could think of that might happen is that the objects would change to solid black (0,0,0 on the RGB scale) with the alpha channel reduced by a certain percentage depending on the lightness/darkness of the shade of gray (which would actually create a transparency it seems to me - a no-no for some book printing vendors). This did not happen, however; the RGB numbers stayed the same and the alpha channel remained at 100% (see below for the numbers).
I now understand that RGB is used for computer graphics while CMYK is used for print graphics. On the RGB scale, I entered 120 for R, G, and B to create a darker gray that I wanted, and 160 each for a lighter shade. I may have also used 80 each a few times.
A moment ago I did a test: in Inkscape, I created a black rectangle, a lighter gray circle (160 RGB each), and a darker gray arc (120 RGB each). I then selected the gray objects and clicked on Extensions>Color>Grayscale. Nothing changed in the RGB panel; the entries were still 120-120-120 or 160-160-160.
So I switched to the CMYK color space panel, selected the lighter gray circle (160 each on the RGB scale), and this showed as cyan=0, magenta=0, yellow=0, and black at 37%. Aside: on other online conversations which discussed K references I did not know what that meant; now I know that it refers to the K (black) in CMYK. No wonder I was confused as to what "K" referred to since I was using RGB which has no K obviously. I assume that the K space is not actually an alpha channel as is the corresponding A channel in RGB even though they both seem to affect transparency.
Another test I did was to create a black circle while in CMYK (0,0,0,100%), and shift the K channel to 37%. No surprise, when switching to RGB it showed 161, 161, 161, with the alpha channel at 100%. What I don't get is that CMYK, RGB, and other color spaces are using different languages/terminology for describing and depicting the very same thing. So if I create an image using RGB, it is automatically formatted accordingly in CMYK as well as all other color spaces. I cannot create a graphic that is ONLY in RGB, or CMYK - so what difference does it make? Perhaps it has to do with the rendering/printing process rather than the creation process, i.e. printers will use the CMYK framework while computer rendering will use the RGB framework.
So if I understand things correctly, for my print book project there is no need to convert my 'RGB' graphics to CMYK to ensure that they are grayscaled - they already are even though I created them using the RGB framework.
Thoughts?
I'd send a pdf test page to the print shop. If they are ok with it and send you a proof that looks right to you, I'd say you're good to go.