C / C++ / MFC

9-Oct-07 23:30

Can anybody help me in converting a 16 bit RGB (555)to 8 bit grayscale bmp.
I got 5 bits of red ,green and blue pixels.

Thanks in advance

CPallini9-Oct-07 23:47

CPallini

9-Oct-07 23:47

Have a look at the following Christian Graus article, here at CP [^]. Porting the grayscale filter algo C# to C++ is straightforward.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Deepu Antony11-Oct-07 8:36

11-Oct-07 8:36

Thanks for helping me it is useful to me

You are welcome

CPallini11-Oct-07 21:07

CPallini

11-Oct-07 21:07

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Nishad S10-Oct-07 0:17

Nishad S

10-Oct-07 0:17

In the 8 bit bmp a color table is used (of size 256 colors). So after you convert the color to gray (using the formula, Y = 0.3R + 0.59G + 0.11B) you have to keep it in a 256 element COLORREF array as a new color if it not added to the array yet. And the index of this array should be saved as the bitmap data. If the color idex is getting overflown ( > 255 ), then the index of a nearest existing color should be identified and the index should be used. For better result, when finding the nearest color, the occurance of that color should be considered. Means if 80% gray is coming 1 time and 81% is coming 20 times, then replacing the 80% to 81% is better. And dont forget to save the created color table also.

- NS -

Deepu Antony10-Oct-07 2:45

10-Oct-07 2:45

Can u make it more clear please..

Nishad S10-Oct-07 3:35

Nishad S

10-Oct-07 3:35

What could you do for this so far?

- NS -

Deepu Antony10-Oct-07 4:40

10-Oct-07 4:40

i seperated red green and blue bits.Thus i have 5 bits of each.then i make it to 8 bit each by shifting them to the left by 3 bits.Then i used the
conversion formula .299*R+.587*G+.114*B .But lost of information is observed.

Is ther is any method to diectly converting it 8 bit grayscale

Mark Salsbery10-Oct-07 6:05

Mark Salsbery

10-Oct-07 6:05

How do you expect to preserve data when converting RGB to
grayscale? It's not going to happen.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Deepu Antony10-Oct-07 17:46

10-Oct-07 17:46

Actually i converted 555 RGB to 888 RGB.Then i converted it to grayScale.Is there is any direct method to convert it to grayscale

Mark Salsbery11-Oct-07 5:34

Mark Salsbery

11-Oct-07 5:34

Deepu Antony wrote:
Is there is any direct method to convert it to grayscale

Not that I know of.

My point was, you're going to lose your RGB data (unless, of course,
you keep it separately).

You stated: "But lost of information is observed"

You can't get the RGB data back once you've converted it.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Deepu Antony11-Oct-07 8:35

11-Oct-07 8:35

i convert 5 bit Green ,5 bit red ,5 bit blue to each 8 bit (24 bit RGB) by shifting it to left by three bits.while doing this loss of information is observed.I know only to convert 24 bit rgb to gray scale.

is there is any direct method to convert 16 bit RBG to 8 bit gray sale.
Can you help me please

[SOLVED] Enabling a button after previous button click.

Mark Salsbery11-Oct-07 8:43

Mark Salsbery

11-Oct-07 8:43

Deepu Antony wrote:
to each 8 bit (24 bit RGB) by shifting it to left by three bits.while doing this loss of information is observed.

There's no loss of information there. You only had 5 bits precision for each color
component to begin with. Widening to 8-bits you still have the same precision.
The image will appear the same on a 16,24,or 32-bitsperpixel display.

Deepu Antony wrote:
s there is any direct method to convert 16 bit RBG to 8 bit gray sale.

The only way I know is the usual luminence formula

intensity = 0.2989*red + 0.5870*green + 0.1140*blue

It yields an eye-pleasing grayscale representation of an RGB image but
no RGB data is preserved.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

char buffers

Programm3r9-Oct-07 23:14

Programm3r

9-Oct-07 23:14

Hi all,

I have a char buffer and a char*
Lets call it:

char buffer[1024];
char* point;

If I perform a strcpy(), and copy the value of the point into the buffer. If the value of the point changes there after, will the value of the buffer change too??

Many Thanks in advance
Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Re: char buffers

Cedric Moonen9-Oct-07 23:17

Cedric Moonen

9-Oct-07 23:17

No, because the pointers points to two different locations. Except if you do something like that:

char* point = &buffer[0];

But then of course, you don't need to use strcpy anymore. strcpy just copy bytes from one memory location to another, it is similar as memcpy (except that it works for null-terminated strings).

Cédric Moonen
Software developer

Charting control [v1.2]

Re: char buffers

Programm3r9-Oct-07 23:30

Programm3r

9-Oct-07 23:30

Thank you Cedric Smile | :)

Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Re: char buffers

David Crow10-Oct-07 3:02

David Crow

10-Oct-07 3:02

Programm3r wrote:
If the value of the point changes there after, will the value of the buffer change too??

Why don't you try it and see? Roll eyes | :rolleyes:

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

CodingLover9-Oct-07 23:14

CodingLover

9-Oct-07 23:14

Hi all,

In my MFC application I've create two buttons, OPEN and CLOSE, used to open a text file and close it. I do it as follows.

<br />
void CSRFToolDlg::OnBnClickedOpen()<br />
{<br />
	char* ReadFileName = "G:\\Work On\\CPP\\SRFTool\\text_file.txt" ; <br />
<br />
	if(openFile.Open(ReadFileName, CFile::modeCreate | CFile::modeReadWrite))<br />
	{<br />
		AfxMessageBox("File creates successfully", MB_OK) ;<br />
	}<br />
	else<br />
	{<br />
		AfxMessageBox("Error in file opening", MB_OK) ;<br />
	}<br />
}<br />
<br />
<br />
void CSRFToolDlg::OnBnClickedClose()<br />
{<br />
	openFile.Close() ;<br />
}<br />

What I want to do is, until user click the Open button the Close button should be disable. How should I do it. Those stuff really new for me.

Thanks Smile | :)

-- modified at 6:08 Thursday 11th October, 2007

I appreciate your help all the time...

Nelek9-Oct-07 23:19

Nelek

9-Oct-07 23:19

Stablish a control member variable to the with the class assistant (ctrl + w, second propertie page) or
use CWindow::GetDlgControl (nID) in order to have access.

Then use EnableWindow (TRUE); //or false as you want

CodingLover9-Oct-07 23:25

CodingLover

9-Oct-07 23:25

Can you explain it with my code. What you mean second property page. I'm unable to found that. Smile | :)

I appreciate your help all the time...

Lakshmi_p9-Oct-07 23:39

Lakshmi_p

9-Oct-07 23:39

hi,
Try this one...
Disable the button in OnInitDialog of your dialog class

eg:
GetDlgItem(UR_CLOSE_BUTTON_ID)->EnableWindow(FALSE);

Enable that button in OnBnClickedOpen function

void CSRFToolDlg::OnBnClickedOpen()
{
char* ReadFileName = "G:\\Work On\\CPP\\SRFTool\\text_file.txt" ;

if(openFile.Open(ReadFileName, CFile::modeCreate | CFile::modeReadWrite))
{
AfxMessageBox("File creates successfully", MB_OK) ;
GetDlgItem(UR_CLOSE_BUTTON_ID)->EnableWindow(TRUE);
}
else
{
AfxMessageBox("Error in file opening", MB_OK) ;
}

}

Again Disable the button in OnBtnClickedClose()

void CSRFToolDlg::OnBnClickedClose()
{
openFile.Close() ;
GetDlgItem(UR_CLOSE_BUTTON_ID)->EnableWindow(FALSE);
}

If you the control variable of Close button, the user that variable in place of GetDlgItem(UR_CLOSE_BUTTON_ID)