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14-Mar-05 22:14

Hi,

My application is doing color dropout from the image and after dropping color only black & white image remains.Here i am using pointer.Firstly i am doing Grayscalling on the image and then doing constrasting my image.I am doing both function in single click but now main problem is that time.It is taking 8-9 seconds for complete whole process.Actually i want that in within 1 second.
Can anybody tell me which one is the best method in C#.net to achieve performance on this task?& why & how to use that method?

thanks

regards.,

Robert Rohde14-Mar-05 23:06

Robert Rohde

14-Mar-05 23:06

Its a bit difficult to help you because you do not exactly explain what you do when grayscaling and contrasting. One hint I can give you is that you should avoid the usage of the Color structure. Both the creation (e.g.Color.FromArgb) and the use of its properties (R, G, B) are relatively heavy functions (at least when using them thousand or millions of times). In one of my projects with bitmap creation and colorcalcluations I could greatly improve perfomance by not using Color. This of course means that you will need to make some implemenations by yourself (e.g. a lightweight structure for exactly your purpose).

Also have a look at NProf. With this tool you can easily find what exactly takes so long in your calculations.

montu337715-Mar-05 0:06

15-Mar-05 0:06

hi,

I really like urs suggestions but is that good way to use multithreading
into R,g,b properties.
my main algorithm is that in doing grayscalling i am taking r,g,b value of each pixel & multipling with .299 for red , .587 for green and .114 for blue and then giving that new value to pixel and this algorithm takes 4 seconds becoz it's calculating thousands of pixels.

Now for doing constrasting it taking another 4 seconds.Here is algorithm.
Now in doing Constrasting,
for each R,G,B if the value is < 0 R/G/B =0 and if value >255 then R/G/B =255
so it is taking another 4 seconds.

Now can u tell me that if i will use multithreading in this both algorithm it will give me more performance or not?
I had not used multithreading ever but as concepts of multithreading is giving faclity for dividine into thread i am hoping from multithreading.

so multithreading will work or not here?

or can u tell me which good approach will help me here.

montu3377

Robert Rohde15-Mar-05 5:30

Robert Rohde

15-Mar-05 5:30

On most processors multithreading wont to do much here. Processors with Hyperthreading would probably gain a bit. You should wait with this until those multicore processors arrive Smile | :)

Are you suing the BitmapData class to get and set the pixel values? If not you should consider doing so.
The first part of your algorithm shouldnt work with floating points. Instead I would try to use integer arithmetic (instead of r = r * 0.299 try r = r * 299 / 1000).
The second part isnt clear for me. Why should the value be < 0 ? Confused | :confused:

If you like send me (part of) your code (for me its fun doing performance tweaks) to treborg@freenet.de.

mav.northwind15-Mar-05 1:54

15-Mar-05 1:54

Hi!
Christian Graus has written a series of articles on image processing.
You could take a look here: Image Processing for Dummies with C# and GDI Pt.1[^]

Regards,
mav

montu337715-Mar-05 2:00

15-Mar-05 2:00

Hi,

thanks but i am using same code as he had given but here for completation of whole thing it takes 8 seconds.
So do u feels that multithreading is best approach for color dropout for making it possible in 1 second.?

mav.northwind15-Mar-05 2:21

15-Mar-05 2:21

I don't know if multithreading will be of much help here, but I've got an additional link for you: Unsafe Image Processing[^].

With just a quick look at Christian's code I think he's using a similar approach, but in the MSDN article there's an additional optimization that's reducing the time to grayscale an image from 14 seconds (pure C# without unsafe code) to ~0.5 seconds, without further voodoo like multithreading.

mav

montu337715-Mar-05 5:16

15-Mar-05 5:16

Hi,

Yeah Excellent i am not having any words for saying thanks to you.You had done great job for me.After reading this article and now i am tring to implement it so most probably i will do colordropout in 1-2 seconds due to this articles.

thanks a lot to You.

montu337715-Mar-05 8:56

15-Mar-05 8:56

Hi,

I really like that article for performance so from that i had implemented Grayscale in 1 second but now contrasting function is taking 4 seconds so whole color filter takes 5 seconds.

so do you have any clue or idea?how to improve that?

mav.northwind15-Mar-05 20:30

Closing the Child Window(popup window)

15-Mar-05 20:30

Hi!

How about adding your contrast calculation in the loop where you're grayscaling the image?
That way you don't have to iterate over all the pixels twice.
Something like this:

PixelData* pPixel = PixelAt(0, y);
for (int x = 0; x < size.X; x++)
{
  byte value = 
  (byte) ((pPixel->red + pPixel->green + pPixel->blue) / 3);
 
  // perform contrast enhancement here:
  value = (value < threshold) ? byte.MinValue : byte.MaxValue;
 
  pPixel->red =  value;
  pPixel->green = value;
  pPixel->blue = value;
  pPixel++;
}

mav

Prabhakar.A14-Mar-05 19:52

Prabhakar.A

14-Mar-05 19:52

Hi,
I Have A parent window in that by pressing a HOTKEY A window(navigating window) opens By Pressing the Link in the Hotkey window it navigates to another page.My Question is If I defaultly closing The Parent window(i.e main window) The hotkey window(navigating) also must Be closed
Rose | [Rose]

Prabhakar.A
Software Engineer

Re: Closing the Child Window(popup window)

mav.northwind14-Mar-05 20:20