Comments on: All about pixel colors: Reference information

By: Steve

Steve — Fri, 05 Dec 2008 12:16:56 +0000

Masoud—1. You picked the slice and changed the pixels, so you must have enough information to determine where they are. 2. No. I don’t know what exactly you mean by “3D graph,” but setting the CData property on an image object, which in Handle Graphics is a 2D thing, won’t affect your 3D image.

By: Masoud

Masoud — Fri, 05 Dec 2008 10:34:15 +0000

Thank you for this summary
I used “slice” command to see a special part from a special direction of a 3D image and I used CData to analyze my image in a 2D gray level matrix.
I manipulated the 2D image(make some pixels blue) and then used “set(h,’CData’,MyImage)” to map it back to the 3D graph.

1. How can I find the position of those blue pixels in 3D space?

2. Does the new changes affect the original 3D Image?

Thank you

By: Steve

Steve — Mon, 07 Jul 2008 13:22:17 +0000

Jonathan—Your desired color scaling goes beyond the scaling supported directly by the Handle Graphics image. You’ll have to write your own scaling function to convert your matrix to an RGB image.

By: Jonathan Bar-on

Jonathan Bar-on — Mon, 30 Jun 2008 16:30:39 +0000

Thanks for the summary but I’m still having trouble with a colormap scaling problem. I have a matrix where I have distinct integer values and I would like to assign a specific color to each value and then display the matrix using image. For example, suppose that my matrix has values (and assigned colors) of 10 – red, 100 – blue, 1000 –black, and 1e8 white while values from 1e5-1e7 are scaled from orange to white. If colormap were n x 4 as opposed to n x 3 then it would be pretty easy to do (one column represents the appropriate scaling). However, this isn’t the case and I can’t figure out how to do what I want using CData or CDataMapping. Any suggestions?

Thanks,

Jonathan Bar-on

By: Dave Watson

Dave Watson — Tue, 01 Apr 2008 20:15:46 +0000

Steve, ignore second question, thanks.

By: Steve

Steve — Tue, 01 Apr 2008 19:18:29 +0000

Dave—Good questions. 1. Unfortunately the answer is yes, that’s expected behavior. However, I anticipate that we’ll soon be able to do a better job with (u)int32 image CData. 2. No.

By: Dave Watson

Dave Watson — Tue, 01 Apr 2008 18:40:04 +0000

Steve, thanks for summarizing. Two questions:

1. When I use (u)int32 data it seems CData gets converted to double. Expected behavior?

2. Is there a way, short of rescaling CData before assigning to the image object, to have the values point to a section of the figure colormap, instead of spanning the entire colormap?

Thanks,