Normalized RGb(passing floating point number)

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HI I am trying to convert an image into normalized rgb now my code is. Folowing code is in the loop equal to image dimensions

C#

     Color color = grayScale.GetPixel(xCoordinate, yCoordinate);
                    sum = (color.R + color.G + color.B);
                    red = color.R;
                    green = color.G;
                    blue = color.B;

                   
                        redColor =  (double)red/ (double)(sum);
                        greenColor = (double)green / (double)(sum);
                        blueColor = (double)blue /(double)(sum);

//Color.FramArgb only accepts int and my val;ues are in double since they are normalized b/w 0-1 
                        grayScale.SetPixel(xCoordinate, yCoordinate,          Color.FromArgb(redColor, greenColor,blueColor));
                     
                    }

now the problem is how can i pass this argument since i cannot convert it to int because i would loose my value.?
Thanks anyways

Posted 9-Jan-14 10:45am

loraloper_22

Updated 9-Jan-14 10:48am

Matt T Heffron

v2

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Ron Beyer 9-Jan-14 16:49pm

Pass what argument? The color? The components? The image?

2 solutions

Solution 2

GetPixel is WAY to slow. Search the articles here for "Image processing for dummies". Yes, you read that right. There's an example in those articles that demonstrates a far faster method of converting an image to grayscale.

Posted 9-Jan-14 10:53am

Dave Kreskowiak

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loraloper_22 9-Jan-14 17:01pm

Yes i know about Lockbit method i was just wondering how to solve that particular problem. Thanks anyways

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Matt T Heffron · Accepted Answer · 2014-01-09T10:49:00

Solution 1

multiply by 255:

C#

grayScale.SetPixel(xCoordinate, yCoordinate, Color.FromArgb((int)(255*redColor), (int)(255*greenColor),(int)(255*blueColor)));

Posted 9-Jan-14 10:49am

Matt T Heffron

Comments

loraloper_22 9-Jan-14 16:53pm

Thank you so much... should have done it myself :)...

Matt T Heffron 9-Jan-14 17:03pm

You're going to discover that your calculations do not create gray scale!
In gray scale all three of R,G,B would be equal.
The simplest calculation would be just the average of the RGB => gray = (R + G + B)/3
This is a kind of gray scale but it doesn't take into account the way that the human eye responds to color, so it will appear wrong.
See: http://en.wikipedia.org/wiki/Gray_scale#Converting_color_to_grayscale

loraloper_22 9-Jan-14 17:08pm

i know this is not going to create a greysclae i just unconsciously named it grey scale. Thanks for pointing this out.
One last question what should i do when any of the RGB component is zero i mean i cannot divide there. Any suggestions?

Matt T Heffron 9-Jan-14 17:21pm

You're only in trouble if sum == 0
Just check for that special case.
0/(not-zero) is OK
In fact, your calculations look to me as if you'll end up with pretty much the same colors as you started with.

loraloper_22 9-Jan-14 17:37pm

Yeah i have added a special case.
"In fact, your calculations look to me as if you'll end up with pretty much the same colors as you started with."
Well i am not having same colors as is started with. Do you think i am normalizing the image in a wrong way?
anyways thanks a lot for you help

Matt T Heffron 9-Jan-14 17:52pm

What you are doing is expanding the color of each pixel independently.
E.g., a nearly black pixel of (1,0,0) would end up as full intensity red.
If you are trying to expand the range of the image as a whole, you probably want to do something like normalize by the maximum sum in the whole image.
Again, see the "Image processing for dummies" article(s) for other operations.

loraloper_22 9-Jan-14 18:50pm

"What you are doing is expanding the color of each pixel independently."|
This is what exactly i am trying to achieve.