stop Refreshing of images drawn by setpixel() and saving it how to do?

Code:

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ONDRAW(CDC *pDC)
for(int y=0; y<=600; y++)
 {
        for(int x=0; x<=600; x++)
        pDC->SetPixel(x,y,RGB(0,255,0));
 }

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This code draw a rectange of green colour. This image gets refreshed everytime whenever it is resized.
As far as i could knoew is WM_PAINT is ahandler which call ONDRAW() through ONPAINT().. Correct me if I am wrong.

Now How do i avoid this refreshing of images. also How will I save this bitmap image generated using setpixel(). Please any one could suggest me and help me out.

FYI I am a learner in visual C++ and I am learning it by solving some of my own problems and examples framed by myself.

Wether it is possible or not?? I am waiting for some ideas or hints or some understanding..

Why are you setting it pixel by pixel ? With FillSolidRect you can do the same, and it's MUCH faster.

Quote:

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Originally Posted by Skizmo

Why are you setting it pixel by pixel ? With FillSolidRect you can do the same, and it's MUCH faster.

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I know that but my purpose is difeerent. Say i am plotting based on a data a 2-d contour plot I have to go pixel wise since i have data at each point ie pixel. At that moment i cannot avoid it. Can you or any please suggest any solution or idea

You should read about flicker-free drawing using double buffering.
In short, you plot your data on the off-screen DC and use BitBlt() in your OnDraw() to paint it on screen.
You would also need to handle WM_ERASEBACKGROUND message to preventing that erase background.

Quote:

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Originally Posted by tarkes

... Now How do i avoid this refreshing of images. ... As far as i could knoew is WM_PAINT is ahandler

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The whole purpose of the WM_PAINT handler is to refresh the image. So why do you want to avoid it?

Quote:

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Originally Posted by tarkes

... also How will I save this bitmap image ...

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This is an entirely different question. Solve your first question first, since it doesn't make sense to save something that isn't what you want. After you solve your first question, then perhaps Google for the CImage class, which might help you.

Mike

Quote:

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This is an entirely different question. Solve your first question first

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Actually... if he has the answer to this question, he can solve the problem of the first question. My guess about why he wants to avoid the refresh is that the SetPixel function is horribly slow. So if he knows how to write it to an image and use that as a cached image, the problem of the slow SetPixel will be gone ;)

Aha, I see. I think you're right. I interpreted his mention of "save" as in a "save to disk", not a "save in memory for a quick re-draw".

Mike

@tarkes, assuming that Skizmo is right (he usually is), then you might still benefit from the CImage class mentioned above, see http://msdn.microsoft.com/en-us/libr...ea7by5(v=vs.80)

The idea is this: Let a CImage object be a member of your class. Draw your 2-d contour into the CImage using CImage::SetPixel. This needs to be done only once. Then, in your OnDraw handler for WM_PAINT, call CImage::BitBlt to blt the contents of the CImage bitmap into the device context provided.

Mike

Assuming skizmo isn't right :p

Windows will trigger a WM_PAINT message whenever something has happened that has invalidated any part of the window.
If you size the window (smaller or larger), then the default behaviour of Windows isi that the entire window will be marked invalid.
If some other window is overlapping your window and that window gets moved, again, that part of the window will be invalidated.
If your window has scrollbars, and the scrollbars are pressed that invalidates the window.
And finally, your own program can explicitely invalidate parts of a window via the InvalidateRect() function.

When a part of a window is invalid, a WM_PAINT will be "in the queue" (it isn't actually there).

You seem to be using MFC, so this WM_PAINT is usually handled in OnPaint, for some controls, MFC will do some preliminary work for you, and you have a somewhat simpler OnDraw() function to do your drawing stuff.


Now... All that stuff above about part of a window getting invalidated... you can override this default behaviour and prevent this invalidation. THe problem of course is that this will make your application look somewhat funny/weird, unless you also do "something" in the areas that would have been invalidated. Applications can use this behaviour to prevent flicker and get more performance by not having to redraw bits of the screen that don't need to be repainted.
It is a somewhat more advanced topic, and not something for a learning programmer, you need a substantial amount of code in place (several hundred lines of code at least) to handle all the special cases.


That said.
SetPixel is really really really slow. The solution is indeed to make a bitmap, and twiddle the bits in this bitmap, and paint the bitmap with BitBlt as it is needed. CImage is one way to to it. If you can't afford to use GDI+, the other way would be to use CreateDIDSection().

Quote:

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Originally Posted by MikeAThon

Aha, I see. I think you're right. I interpreted his mention of "save" as in a "save to disk", not a "save in memory for a quick re-draw".

Mike

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There has been lot of discussion goin on these. Soory I was bit out for 2 days. I was not in a position to check the post.
My aim is:
1. Display the image without refreshment i.e. what save in cache memory and display.

2. Save into disk if it is possible so.

3. Presence of scroll bar in window if the image is large than SDI window.

I have not read the posts thourughly. Let me go through it and get some hints if possible.

Unfortuanately I am using VC++ 6.

http://social.msdn.microsoft.com/For...8-9a09af6044e5

What is find there is no CImage class being defined in VC++ 6. Can anyone suggest me in regard to this.
Waiting for any reply

1) This requires a "off screen bitmap" which you then blit to screen.
It avoids the whole pixel by pixel thing entirely.

2) THen I'd go with the CImage GDI+ solution posted. You can do this with the CreateDIBSection() solution also, but saving an image that's usuable/displayable in other programs is a bit more complex.

3) I would recommend you look at the CScrollView class as base class for your SDI window. This'll take care of most of the scrolling stuff for you. All you need to do is set your desired size (600x600), and you provide the OnDraw function, MFC will take care of the rest adequately enough for a starter program. Though you can improve on what it does.

for VC++ 6.
You can still make use of gdi+, you just need to have the headers and library installed.
http://www.microsoft.com/en-us/downl....aspx?id=18909

Quote:

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Originally Posted by OReubens

for VC++ 6.
You can still make use of gdi+, you just need to have the headers and library installed.
http://www.microsoft.com/en-us/downl....aspx?id=18909

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I had downladed the setup filw which is of 852kb. what should be the directory of setup. and for a trial i just extracted it but i dont find any header files .h as such. please kindly can u assist me

hmm actually this may be harder than I thought... The headers are part of the platform SDK. but I'm not sure microsoft still distributes platform SDK's compatible with VC6.
THe newer ones won't work for sure because VC6 isn't c++ standards compliant.

You really should consider upgrading to a newer version of VC.
In any case, even if you do find a platform SDK with GDI+ support that works for VC6. CImage (an MFC class) won't work on VC6. you can use the GDI+ primitives of course.

since all you need of gdi+ is the bitmap thing... this'll probably be easier to get to work using the CreateDIBSection() solution instead.

Create a new project.
Set the type to SDI.
Set the view type to CScrollview

Open the view header and add the following 2 members.

Code:

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CBitmap m_Bmp;
DWORD* m_pdwBits;

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In the OnDraw() you add this code

Code:

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        CDC dcMem;
        dcMem.CreateCompatibleDC(pDC);
        CBitmap* pOldBmp = dcMem.SelectObject(&m_bmp);
        BITMAP bmpInfo;
    m_bmp.GetBitmap(&bmpInfo);
        pDC->BitBlt(0,0,bmpInfo.bmWidth,bmpInfo.bmHeight,&dcMem, 0,0, SRCCOPY);
        dcMem.SelectObject(pOldBmp);

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In the OnInitialUpdate() set the sizeTotal variable to the desired size (600x600) and add following bit of code:

Code:

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        BITMAPINFO bmi;
        memset(&bmi, 0, sizeof(BITMAPINFO));
        bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
        bmi.bmiHeader.biWidth = sizeTotal.cx;
        bmi.bmiHeader.biHeight = -sizeTotal.cy; // top-down
        bmi.bmiHeader.biPlanes = 1;
        bmi.bmiHeader.biBitCount = 32;
        bmi.bmiHeader.biCompression = BI_RGB;
        m_bmp.Attach( CreateDIBSection( *GetDC(), &bmi, DIB_RGB_COLORS, (void**)&m_pdwBits, NULL, NULL) );
        ZeroMemory(m_pdwBits, sizeof(sizeTotal.cx*sizeTotal.cy*sizeof(DWORD)));

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You can then use the m_pdwBits variable as a simple bitmap. each "pixel" is a 32bit RGB pixel in ARGB format.
to set a pixel at 100x50 to purple.
m_pdwBits[ 100*600 + 50 ] = 0x00FF00FF; // set red and blue to 255.

be careful not to write outside of your given size.
With the above code, 0,0 of the bitmap will be located at the top left of the window, with increasing Y pointing downward
If you'd like it at the bottom left with increasing Y going upward. set biHeight to the poxitive value rather than the negative one.

When you have made changes to the bitmap and want to see them. Invalidate the window with Invalidate();