passing images as arguments

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Hello,I want to pass few images as arguments but when done,all the images get the same value.here is some of my codes.please help me,thanks in advance

MIDL

Bitmap[] ima = new Bitmap[20];
           ima[0] = new Bitmap(Main_P.Image);
           ima[1] = gray(ima[0]);//Setting the picture trough gray scale
           ima[2] = noise(ima[1]);
           ima[3] = histogram(ima[2]);
           ima[4] = binary(ima[3]);
           ima[5] = reverse_binary(ima[4]);
           ima[6] = distance2(ima[5]);
           ima[7] = max2(ima[6]);
           ima[8] = extension_binary(ima[7]);
           ima[9] = complementary_0f_distance(ima[6]);
           ima[10] = apply_sign_image_to_basis_image(ima[9], ima[8], ima[5]);




          Main_P.Image =(Bitmap)ima[7];

here all the images get the same value!

Posted 30-Jun-11 4:15am

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fjdiewornncalwe · Accepted Answer · 2011-06-30T04:25:00

Solution 1

It is likely that your issues aren't in how you pass the images as arguments, but rather what you do with them in the functions you are sending them to. Remember that arguments are being sent as references so that anything you do to manipulate the argument will affect all references to it.

Posted 30-Jun-11 4:25am

fjdiewornncalwe

Comments

ready to learn 30-Jun-11 10:34am

do you mean that if I want to pass the bitmap it will be passed by refrence?notice that I didn't use "Ref".

fjdiewornncalwe 30-Jun-11 23:03pm

It is important to know that in C#, objects are passed by reference whether you specify the ref keyword or not on them.

Sergey Alexandrovich Kryukov 1-Jul-11 23:40pm

My 5. It looks like OP needs to learn a fundamental idea: reference types vs value types and their implications.
--SA

wizardzz · Accepted Answer · 2011-06-30T04:26:00

Solution 2

Is it possible that these functions you are calling are modifying the value of the passed params as well as returning them. Could you post the code of one?

Posted 30-Jun-11 4:26am

wizardzz

Comments

ready to learn 30-Jun-11 10:32am

sorry this is true:
private Bitmap gray(Bitmap bm)
{
st_g.Start();
int cal;
BitmapData bmdata = bm.LockBits(new Rectangle(0, 0, bm.Width, bm.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
IntPtr scan0 = bmdata.Scan0;
int stride = bmdata.Stride;
unsafe
{
byte* p = (byte*)(void*)scan0;
int offset = stride - (bm.Width * 3);
for (int i = 0; i < bm.Height; i++)
{
for (int j = 0; j < bm.Width; j++)
{
cal =Convert.ToInt32( (p[0] + p[1] + p[2])/3);
p[0] = p[1] = p[2] = (byte)cal;

p += 3;
}
p += offset;
}
}
bm.UnlockBits(bmdata);
st_g.Stop();
return bm;
}

wizardzz 30-Jun-11 10:37am

Yeah, you are returning the passed parameter after modifying it.

ready to learn 30-Jun-11 10:40am

can you please change the code so that this problem doesn't take place?I return the image in another one

BobJanova 30-Jun-11 11:01am

Try using Image.Clone first in each function, e.g.

private Bitmap gray(Bitmap bm)
{
bm = (Bitmap)bm.Clone(); // ADD THIS

st_g.Start();
int cal;
BitmapData bmdata = bm.LockBits(new Rectangle(0, 0, bm.Width, bm.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
...
}

ready to learn 30-Jun-11 11:08am

thanks a lot.I think it works

wizardzz 30-Jun-11 11:15am

You're welcome. Can you mark my solution as accepted please?

wizardzz 30-Jun-11 12:37pm

By accepting the answer, I mean can you mark it as accepted on the website? Otherwise the question remains open, others may waste time answering, and I lose out on some points.

Sergey Alexandrovich Kryukov 1-Jul-11 23:42pm

OP is recommended to accept both answers: this one and the one by Marcus (please see also my comment to his answer).
I voted 5, good catch; it tool patience.
--SA