Expert: Ran - 5/9/2009

Question
QUESTION: Hi Again Ran....I am trying to make a greyscale wall mural from a photograph.  I import the photo I intend to use then adjust its color to greyscale.  Is there an operation I can do which tells me how many different shades are in the bitmap?  How many and which greys were used to create the greyscale image....?

ANSWER: Hi Alice

When I convert an image to greyscale in CorelDraw I use Bitmaps/Convert to Bitmap. The Greyscale option states "(8-bit)".

What this means, is that each grey pixel will be represented by 8 data bits, where each bit is either a binary (base 2) zero or one. So you have a fixed number of mathematical permutations ranging from:

00000000 which in decimal (base 10) is still 0
(this represents black because the zero directly relates to the brightness of the pixel displayed on the screen)

to

11111111 which in decimal is 255 and in hexadecimal (base 16) is FF
(white)

The total number of permutations of 8 binary digits, counting zero, therefore is 256. Your converted photo will almost certainly contain all 256 of these greyscales. If you converted an image with a smooth gradient from black to white and looked closely at it, it would contain 256 "fountain steps".

Your image will be stored on the hard drive of your PC as a sequence of these 8-bit 'words', each of which is called a byte.

I'm sure this is much more information than you need, but understanding the above may assist you in other areas you will come across in the future.

To locate any colour in particular in Draw X4, open the Bitmap Colour Mask docker (on the Bitmaps menu) and click the eyedropper button. Click the grey you want to inspect on your image, then click the Edit Colour button, next to the eyedropper.

This opens up the Select Colour dialog, where you can see the figures for your chosen greyshade. In Model, select Greyscale to keep things simple. On the grey pixel I clicked, its colour was 98 (out of 255).

I apologise for any confusion you might feel with the way I spell COLOUR and GREY. This is because I only speak English!

---------- FOLLOW-UP ----------

QUESTION: Hi Ran - no problem with your syntax as I've grown up in both Canada and the States....and details are a good thing for me.  If I don't use them now I will most certainly use them later....Yes, I was aware of greyscale being 8bit (256 colours).  I don't suppose there is a dialog available in which you can specify a limit to which greys are used or how many greys are used.  I would like to be able to specify only say, 10 different greys for this particular picture.....can THAT be done?

ANSWER: Convert your image to Greyscale.
Choose Bitmaps/Outline Trace/Detailed Logo.
Muck around in the PowerTRACE dialog to get the effect you need.
Be patient - I have a quad-core Xeon 3GHz PC and it takes a while to process!
Limit the number of colours/greyscales on the Colours tab.

This is actually my second answer to this question (I deleted the first, because initially I thought I couldn't do what you wanted without using Photoshop first - der!)

---------- FOLLOW-UP ----------

QUESTION: Hey Ran - thanks for the answer and the advice.  Never thought to do it that way.  I'm curious about something though - you've answered questions for me before where you suggest using Photoshop.  Don't you use Corel-PAINT? If not why not?  I'm just learning how to use that as well and I was under the impression that it is a compatible program to Photoshop....

Answer
Hi again Alice

I've not installed CorelPaint because I've used Photoshop for many years now. Both will have a similar learning curve so given the choice between the two I'd choose to invest my time learning Photoshop, purely for the reason that it is currently the industry standard.

Previously I'd considered swapping our graphics dept over to Illustrator instead of CorelDraw for the same reason. However although Illustrator has improved a lot I don't think it holds a candle to X4. One simple example being the way Illustrator selects objects when you draw a marquee. It selects everything you touch, whereas CorelDraw selects only what you completely enclose. I found the Illustrator way makes it very fiddly to select things close together in a complex drawing. It doesn't sound much, but when you're doing it 2-300 times every day it could rapidly destroy your will to live. And I don't like all the floating palettes either.

So, when people ask me PhotoPaint questions, can I forward them to you?