urgent help pleasse [image processing , pointers , byte ]

[WinSolution]

Hi Everyone please look at following two line this is not working when i execute my prject int div = Convert.ToInt32(textBox1.Text.Trim()); ptr[0] = ptr[1] = ptr[2] = (byte)((ptr[0] + ptr[1] + ptr[2]) / div); but if i remove the first line and enter an integer value in place of div variable it works such as following line. ptr[0] = ptr[1] = ptr[2] = (byte)((ptr[0] + ptr[1] + ptr[2]) / 3); Following is the full listing may it help you to figurout the problem a method that convert a bitmap from colored to grayscale ////////////////////////////////////////////////////////////////////////// public Bitmap GrayScale(Bitmap bmpimg) { BitmapData bmpData = bmpimg.LockBits(new Rectangle(0, 0, bmpimg.Width, bmpimg.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int remain = bmpData.Stride - bmpData.Width * 3; unsafe { byte* ptr = (byte*)bmpData.Scan0; for (int i = 0; i < bmpData.Height; i++) { for (int j = 0; j < bmpData.Width; j++) { int div = Convert.ToInt32(textBox1.Text.Trim()); ptr[0] = ptr[1] = ptr[2] = (byte)((ptr[0] + ptr[1] + ptr[2]) / div); ptr += 3; } ptr += remain; } } bmpimg.UnlockBits(bmpData); return bmpimg; }

[Luc Pattyn]

:confused: :confused: :confused: why is int div = Convert.ToInt32(textBox1.Text.Trim()); inside the nested loops? Are you planning on changing div while the image processing is going on? or are you just looking for ways to make it extremely slow? :)

Luc Pattyn [Forum Guidelines] [My Articles]

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[Henry Minute]

WinSolution wrote:

this is not working when i execute my prject

What does this mean? Are you getting an exception? Does it do something you do not expect? Have you single stepped, to see what value div is set to in your code? What, which, something else? BTW there are several articles here on CP that demonstrate converting to greyscale, have you looked at them.

Henry Minute Do not read medical books! You could die of a misprint. - Mark Twain Girl: (staring) "Why do you need an icy cucumber?" “I want to report a fraud. The government is lying to us all.”

[WinSolution]

Thanks both problem solved i was not handling exception and not i placed that code outside of the loops as follow public Bitmap GrayScale(Bitmap bmpimg) { BitmapData bmpData = bmpimg.LockBits(new Rectangle(0, 0, bmpimg.Width, bmpimg.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int remain = bmpData.Stride - bmpData.Width * 3; unsafe { byte* ptr = (byte*)bmpData.Scan0; int div = 1; try { div = Convert.ToInt32(textBox1.Text.Trim()); } catch (Exception ex) { MessageBox.Show(ex.Message); } for (int i = 0; i < bmpData.Height; i++) { for (int j = 0; j < bmpData.Width; j++) { ptr[0] = ptr[1] = ptr[2] = (byte)((ptr[0] + ptr[1] + ptr[2]) / div); ptr += 3; } ptr += remain; } } bmpimg.UnlockBits(bmpData); return bmpimg; }

[Luc Pattyn]

Hi, when you store the value of bmpData.Width in a local variable, your code will run some 20% faster. :)

Luc Pattyn [Forum Guidelines] [My Articles]

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[Christian Graus]

WinSolution wrote:

div = Convert.ToInt32(textBox1.Text.Trim());

You should use int.TryParse to test if the entered text is a number or not.

Christian Graus Driven to the arms of OSX by Vista. "! i don't exactly like or do programming and it only gives me a headache." - spotted in VB forums. I can do things with my brain that I can't even google. I can flex the front part of my brain instantly anytime I want. It can be exhausting and it even causes me vision problems for some reason. - CaptainSeeSharp

[saurabh sahay]

You may also handle the exception for ptr[0] = ptr[1] = ptr[2] = (byte)((ptr[0] + ptr[1] + ptr[2]) / div);