C / C++ / MFC

Re: dll creation in win32

3-Mar-09 23:25

It's not a problem with the class. Can you send your solution (lib's) to dejavunic_at_gmail ?

He never answers anyone who replies to him. I've taken to calling him a retard, which is not fair to retards everywhere.-Christian Graus

Hamid_RT3-Mar-09 19:08

Hamid_RT

3-Mar-09 19:08

How to Create a Simple Win32 DLL [^].

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For all Others to feel the Mace
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Convert 16bit grayscale bitmap to 8bit grayscale bitmap

Akt_4_U3-Mar-09 18:12

Writing 8-bit grayscale bitmap data

3-Mar-09 18:12

Hi All,

How can I convert an 16bit grayscale bitmap to 8 bit grayscale bitmap?

Thanks

akt

Member 21167363-Mar-09 17:36

3-Mar-09 17:36

Hi everybody,

I'm currently working with 8-bit grayscale bitmap scanned from my HP LaserJet 3055. I am able to read the Bitmap Header and its data into an array of BYTE. I write the values directly into Text File, the result is great! However, I can't create another BMP file using the data array I have.

For 24-bit BMP, what we have to write after the Header is the RGB data, but for the grayscale one we have to use the Color Table, right? How can I use the Color table properly?

Please anyone helps me on how to create an 8-bit grayscale bitmap!

Thanks,

Ing LengIeng
Software Developer

Akt_4_U3-Mar-09 18:08

3-Mar-09 18:08

Hi,

For an 8 bit grayscale image, between the header and pixel data, there will a color map of 256 colors. The color map will hold 256 shades of gray(ie R=G=B).
The actual pixel data will be a reference this color map. So fo creating 8 bit grayscale image do the following steps.

1. Open a file in binary mode.
2. Write Bitmap File header to file.
3. Write Bitmap Info header to file.
4. Write Colormap to file.
5. Write pixel data to file.
6. Close file.

Thanks
Akt_4_U

akt

Member 21167363-Mar-09 21:03

3-Mar-09 21:03

Thanks very much, Akt!

But how do I write the Colormap? I wrote the following code, but I didn't get the grayscale anymore; instead, I got a more green color for the new image.

for(int c=0; c<256; c++)
{
  fwrite((BYTE*)&bmpInfo.bmiColors[c], sizeof(RGBQUAD), 1, bmpFile);
}

Regards,

Ing LengIeng
Software Developer

Akt_4_U3-Mar-09 22:01

3-Mar-09 22:01

Hope you have read the ColorMap completely from source bitmap. That is you have to allocate enough memory for reading the complete ColorMap(256 colors) for source image.
The following code will do this.

BYTE* pbyThumbImage // This is your source bitmap buffer.
const ULONG COLORMAP_START_OFFSET = sizeof( BITMAPFILEHEADER ) + sizeof( BITMAPINFOHEADER ); // Color map starts after Bitmap file header and Bitmap info header.
UINT uColorMapSize = 256 * sizeof( RGBQUAD );
pBmpInfoHdr = reinterpret_cast<lpbitmapinfo>( GlobalAllocPtr( GHND, sizeof( BITMAPINFOHEADER ) + uColorMapSize ));
memcpy( pBmpInfoHdr->bmiColors, ( pbyThumbImage + COLORMAP_START_OFFSET ), uColorMapSize ); // Now complete colormap information is within your pBmpInfoHdr->bmiColors.

Now you can write this colormap to destination file using fwrite with input buffer as pBmpInfoHdr->bmiColors and size to be written as uColorMapSize.

akt

Member 21167364-Mar-09 4:09

4-Mar-09 4:09

But soon after I've finished reading the Colormap, I displayed the value of each RGB I can see that the color itself is of color more than the grayscale. I did so by comparing the RGB I get with the value in Microsoft Paint (mspaint.exe). That's why the result of the new image is rather a color one. How can I solve this?

Ing LengIeng
Software Developer

Akt_4_U4-Mar-09 22:19

4-Mar-09 22:19

Which value did u take? R G and B from color map?

akt

Member 21167364-Mar-09 22:40

how to clear editbox with vc2005

4-Mar-09 22:40

Hi Akt,

Now I've solved my problem. I make the Colormap again by myself through the loop, and write it into the new bmp.

Thanks a lot! Smile | :)

Regards,

Ing LengIeng
Software Developer

chenfengrugao3-Mar-09 17:12

chenfengrugao

3-Mar-09 17:12

Hi all,
I placed two edit boxes and two buttons in my dialog. I want to click the first button to clear the first edit box , and click the second button to clear the second edit box .
In the function of clicking the button, writing the following:

void CSerialPortTestDlg::OnBnClickedClearrec()
{
m_sEditRec.Empty();
UpdateData(0);
}

void CSerialPortTestDlg::OnBnClickedClearsend()
{
m_sEditSend.Empty();
UpdateData(0);
}

However, when I click one button , both edit boxes are cleared!!!

Could someone tell me why ?I write these codes in vc6.0 and it's no problem.

Eytukan3-Mar-09 17:28

3-Mar-09 17:28

It looks like the DDX variable attached to second edit box is empty. So when you make an UpdateData(false), the editbox would get cleared. First save the value into the variable. In this case you might have used a CString. Assign some value for the string. If you want to keep the value that you entered in the edit box, first call UpdateData(true). Then try it wont get cleared.

Also don't save UpdateData(0), looks ugly. use "true-false".

He never answers anyone who replies to him. I've taken to calling him a retard, which is not fair to retards everywhere.-Christian Graus

chenfengrugao3-Mar-09 17:38

chenfengrugao

3-Mar-09 17:38

Thanks a lot! I understand!

David Crow4-Mar-09 3:24

David Crow

4-Mar-09 3:24

This is one of the reasons why UpdateData() should be avoided. Use this instead:

void CSerialPortTestDlg::OnBnClickedClearrec()
{
    m_editRec.SetWindowText("");
}
 
void CSerialPortTestDlg::OnBnClickedClearsend()
{
    m_editSend.SetWindowText("");
}

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Eytukan4-Mar-09 3:27

4-Mar-09 3:27

But this one won't clear the data. So won't that go out of sync, in case if he is using the CString variable after clicking these buttons?

He never answers anyone who replies to him. I've taken to calling him a retard, which is not fair to retards everywhere.-Christian Graus

David Crow4-Mar-09 3:33

David Crow

4-Mar-09 3:33

VuNic wrote:
So won't that go out of sync...

All the more reason to not use UpdateData().

Eytukan4-Mar-09 6:50

4-Mar-09 6:50

You don't recommend DDX as such?

He never answers anyone who replies to him. I've taken to calling him a retard, which is not fair to retards everywhere.-Christian Graus

David Crow4-Mar-09 6:53

David Crow

4-Mar-09 6:53

Not using UpdateData() does not preclude the use of DDX.

Eytukan4-Mar-09 6:54