Programming Forums > Application Development > C++

null_ptr0 · Feb 22nd, 2008, 6:13 PM

I've tried to do CreateCompatibleDC(source_device) but it contains a result the same height and size as source_device but every pixel as black. Any help?

(Toggle Plain Text)

const int SCREEN_WIDTH = GetSystemMetrics(SM_CXSCREEN) - 1;
const int SCREEN_HEIGHT = GetSystemMetrics(SM_CXSCREEN) - 1;
...
    int x;
    HDC screen_device = GetDC(NULL);
    HDC copy = CreateCompatibleDC(screen_device);
    for (x = 0; x <= SCREEN_WIDTH; ++x) {
        for (int y = 0; y <= SCREEN_HEIGHT; ++y) {
            SetPixel(screen_device, x, y,  GetPixel(copy, SCREEN_WIDTH - x, y));
        }
    }
...

EDIT:
I see I have to use BitBlt? If so, may I have an example? I have an inefficiency in understanding win32 argument names.

The Dark · Feb 22nd, 2008, 6:43 PM

You code seems to be setting the pixels in the screen device from the copy, I think it should be the other way around.

Ooble · Feb 23rd, 2008, 6:48 AM

In your second line, you use SM_CXSCREEN when it should be SM_CYSCREEN. I think The Dark found your main problem though.

null_ptr0 · Feb 23rd, 2008, 1:06 PM

Quote:

Originally Posted by Ooble

In your second line, you use SM_CXSCREEN when it should be SM_CYSCREEN. I think The Dark found your main problem though.

aha. thanks.
@The Dark:
My goal is to create a copy of the screen, and then reverse the screen from reversing the pixels on my copy.

Ooble · Feb 23rd, 2008, 1:25 PM

From the CreateCompatibleDC page:

Quote:

A memory DC exists only in memory. When the memory DC is created, its display surface is exactly one monochrome pixel wide and one monochrome pixel high. Before an application can use a memory DC for drawing operations, it must select a bitmap of the correct width and height into the DC. To select a bitmap into a DC, use the CreateCompatibleBitmap function, specifying the height, width, and color organization required.

I'd recommend reading the rest of the stuff under the Remarks heading too.

null_ptr0 · Feb 23rd, 2008, 1:45 PM

your link points to GetDC

edit:
how would i set the newly created HBITMAP's pixels?

Ooble · Feb 23rd, 2008, 2:08 PM

Sorry. Here's the real link.

I believe you can do as you were doing after you call CreateCompatibleBitmap. Don't forget that you have to call it on screen_device and then call SelectObject.

Feb 22nd, 2008, 6:13 PM	#1
null_ptr0 12 years old Join Date: Nov 2007 Posts: 94 Rep Power: 1	[win32][gdi32] Copying HDC to another? I've tried to do CreateCompatibleDC(source_device) but it contains a result the same height and size as source_device but every pixel as black. Any help? (Toggle Plain Text) const int SCREEN_WIDTH = GetSystemMetrics(SM_CXSCREEN) - 1; const int SCREEN_HEIGHT = GetSystemMetrics(SM_CXSCREEN) - 1; ... int x; HDC screen_device = GetDC(NULL); HDC copy = CreateCompatibleDC(screen_device); for (x = 0; x <= SCREEN_WIDTH; ++x) { for (int y = 0; y <= SCREEN_HEIGHT; ++y) { SetPixel(screen_device, x, y, GetPixel(copy, SCREEN_WIDTH - x, y)); } } ... const int SCREEN_WIDTH = GetSystemMetrics(SM_CXSCREEN) - 1; const int SCREEN_HEIGHT = GetSystemMetrics(SM_CXSCREEN) - 1; ... int x; HDC screen_device = GetDC(NULL); HDC copy = CreateCompatibleDC(screen_device); for (x = 0; x <= SCREEN_WIDTH; ++x) { for (int y = 0; y <= SCREEN_HEIGHT; ++y) { SetPixel(screen_device, x, y, GetPixel(copy, SCREEN_WIDTH - x, y)); } } ... EDIT: I see I have to use BitBlt? If so, may I have an example? I have an inefficiency in understanding win32 argument names.

Feb 22nd, 2008, 6:43 PM	#2
The Dark Expert Programmer Join Date: Jun 2005 Posts: 852 Rep Power: 4	Re: [win32][gdi32] Copying HDC to another? You code seems to be setting the pixels in the screen device from the copy, I think it should be the other way around.

Feb 23rd, 2008, 6:48 AM	#3
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: [win32][gdi32] Copying HDC to another? In your second line, you use `SM_CXSCREEN` when it should be `SM_CYSCREEN`. I think The Dark found your main problem though. __________________ Me :: You :: Them

Feb 23rd, 2008, 1:45 PM	#6
null_ptr0 12 years old Join Date: Nov 2007 Posts: 94 Rep Power: 1	Re: [win32][gdi32] Copying HDC to another? your link points to GetDC edit: how would i set the newly created HBITMAP's pixels?

Feb 23rd, 2008, 2:08 PM	#7
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: [win32][gdi32] Copying HDC to another? Sorry. Here's the real link. I believe you can do as you were doing after you call `CreateCompatibleBitmap`. Don't forget that you have to call it on `screen_device` and then call `SelectObject`. __________________ Me :: You :: Them

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Programming Forums > Application Development > C++

[win32][gdi32] Copying HDC to another?