PAINTSTRUCT Ps;
myDC = BeginPaint(myHwnd, &Ps);
MemDC = CreateCompatibleDC(myDC);
SelectObject(MemDC, myBitmap);
BitBlt(myDC, 0, 0, iWidth, iHeight, MemDC, 0, 0, SRCCOPY);
DeleteDC(MemDC);
EndPaint(myHwnd, &Ps);
HBITMAP to Window
Author
hello, im trying to get an HBITMAP to display on my window. I have loaded the image from file and im trying to display it with this..
before, i had read all the RGB values from the HBITMAP and displayed them all using SetPixel(). It was way to slow and im trying to speed up the process.
im not sure where to go from here. can someone give me some guidance.
thanks
From Game Programming Genesis Part III:
Also an alternative to this is to create a PictureBox control as a child of your window, and then give the control your bitmap (the control handles drawing it for you). This is handy for sticking one or two pictures in a dialog box, for instance.
int ShowBitmapResource(HDC hDestDC, int xDest, int yDest, int nResID){ HDC hSrcDC; // source DC - memory device context HBITMAP hbitmap; // handle to the bitmap resource BITMAP bmp; // structure for bitmap info int nHeight, nWidth; // bitmap dimensions // first load the bitmap resource if ((hbitmap = (HBITMAP)LoadImage(hinstance, MAKEINTRESOURCE(nResID), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION)) == NULL) return(FALSE); // create a DC for the bitmap to use if ((hSrcDC = CreateCompatibleDC(NULL)) == NULL) return(FALSE); // select the bitmap into the DC if (SelectObject(hSrcDC, hbitmap) == NULL) return(FALSE); // get image dimensions if (GetObject(hbitmap, sizeof(BITMAP), &bmp) == 0) return(FALSE); nWidth = bmp.bmWidth; nHeight = bmp.bmHeight; // copy image from one DC to the other if (BitBlt(hDestDC, xDest, yDest, nWidth, nHeight, hSrcDC, 0, 0, SRCCOPY) == NULL) return(FALSE); // kill the memory DC DeleteDC(hSrcDC); // return success! return(TRUE);}Also an alternative to this is to create a PictureBox control as a child of your window, and then give the control your bitmap (the control handles drawing it for you). This is handy for sticking one or two pictures in a dialog box, for instance.
Author
im pretty sure its not selected, but if it is already selected, is that why its failing?
A bitmap can only be selected into one context at a time. Other reasons that the call could fail include myBitmap not actually being a valid bitmap or the DC not being a valid DC.
What does your current code look like?
What does your current code look like?
Author
these are functions for loading an image, and also getting rgb values from an HBITMAP
this is my winmain
heres a portion of my WndProc
iWidth, iHeight, myBitmap are globals atm
#ifndef IMAGE_H#define IMAGE_H#include <windows.h>#include <olectl.h> #include <ole2.h>#include "Color.h"HBITMAP LoadAnImage(const char*);ColorRGB* GetImageInfo(HBITMAP bmp, int* w, int* h){ //variables BITMAP bm; COLORREF Color; int width, height; int R, G, B; int pixelCount, count = 0; //load image HDC dc = ::GetDC(0); HDC MemDC = ::CreateCompatibleDC(dc); HANDLE hBMP = bmp; HBITMAP hOldBmp = (HBITMAP)::SelectObject(MemDC,hBMP); //get width height GetObject(hBMP, sizeof(BITMAP), (LPVOID)&bm); width = bm.bmWidth; height = bm.bmHeight; pixelCount = width*height; ColorRGB* imgRgbTable = new ColorRGB[pixelCount]; for (int i = 0; i < height; i++) { for (int y = 0; y < width; y++) { Color = ::GetPixel(MemDC,y,i); // X,Y R = GetRValue(Color); G = GetGValue(Color); B = GetBValue(Color); imgRgbTable[count].SetRGB(R,G,B); count++; } } ::SelectObject(MemDC,hOldBmp); ::DeleteObject(hBMP); ::DeleteDC(MemDC); ::ReleaseDC(0,dc); /*debug for (int i = 0; i < pixelCount; i++) cout << "R: " << imgRgbTable.R << " - G: " << imgRgbTable.G << " - B: " << imgRgbTable.B << endl; */ *w = width; *h = height; return imgRgbTable;}HBITMAP LoadAnImage(const char* FileName){ // Use IPicture stuff to use JPG / GIF files IPicture* p; IStream* s = NULL; IPersistStream* ps = NULL; HGLOBAL hG; void* pp; FILE* fp; // Read file in memory fopen_s(&fp, FileName,"rb"); if (!fp) return NULL; fseek(fp,0,SEEK_END); int fs = ftell(fp); fseek(fp,0,SEEK_SET); hG = GlobalAlloc(GPTR,fs); if (!hG) { fclose(fp); return NULL; } pp = (void*)hG; fread(pp,1,fs,fp); fclose(fp); // Create an IStream so IPicture can CreateStreamOnHGlobal(hG,false,&s); if (!s) { GlobalFree(hG); return NULL; } OleLoadPicture(s,0,false,IID_IPicture,(void**)&p); if (!p) { s->Release(); GlobalFree(hG); return NULL; } s->Release(); GlobalFree(hG); HBITMAP hB = 0; p->get_Handle((unsigned int*)&hB); // Copy the image. Necessary, because upon p's release, // the handle is destroyed. HBITMAP hBB = (HBITMAP)CopyImage(hB,IMAGE_BITMAP,0,0, LR_COPYRETURNORG); p->Release(); return hBB;}this is my winmain
int APIENTRY _tWinMain(){ myBitmap = LoadAnImage("C:\\Users\\BigJoe\\Desktop\\test.bmp"); myRgb = GetImageInfo(myBitmap, &iWidth, &iHeight); //setup window gui and create root folder myGui = new ScanGUI("Image Scanner", iWidth, iHeight); myGui->InitWindow(); MSG msg = {0}; while (WM_QUIT != msg.message) { while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE) == TRUE) { TranslateMessage(&msg); DispatchMessage(&msg); } } return 0;}heres a portion of my WndProc
case WM_PAINT: HDC hSrcDC; // source DC - memory device context // create a DC for the bitmap to use if ((hSrcDC = CreateCompatibleDC(myDC)) == NULL) return(FALSE); // select the bitmap into the DC if (SelectObject(hSrcDC, myBitmap) == NULL) return(FALSE); // copy image from one DC to the other if (BitBlt(myDC, 0, 0, iWidth, iHeight, hSrcDC, 0, 0, SRCCOPY) == NULL) return(FALSE); // kill the memory DC DeleteDC(hSrcDC);iWidth, iHeight, myBitmap are globals atm
Some comments:
LoadAnImage() - why not just use LoadImage()?
GetImageInfo() - the bmBits members of the BITMAP struct has the RGB information
As for the problem:
Your WM_PAINT handler is incorrect. You should get dcSrc from BeginPaint() and let EndPaint() do what it wants to it. Create a compatible memory DC and select myBitmap into that - remembering of course to store the returned HBITMAP. Use BitBlt() from the memory DC to dcSrc. The select the stored HBITMAP back into the memory DC so that your bitmap is no longer in it and delete the memory DC.
LoadAnImage() - why not just use LoadImage()?
GetImageInfo() - the bmBits members of the BITMAP struct has the RGB information
As for the problem:
Your WM_PAINT handler is incorrect. You should get dcSrc from BeginPaint() and let EndPaint() do what it wants to it. Create a compatible memory DC and select myBitmap into that - remembering of course to store the returned HBITMAP. Use BitBlt() from the memory DC to dcSrc. The select the stored HBITMAP back into the memory DC so that your bitmap is no longer in it and delete the memory DC.
LoadImage can't load JPEG and GIF files.
My quess as Colin suggests (but I'll put a finer point on it) is that this code works ONCE on the first draw but it gets redrawn so fast that the bug you have in your code isn't obvious.
When you SelectObject(MemDc, myBitmap) you need to store the returned HBITMAP. Then after you are done with BitBlt() SelectObject(MemDc, oldBitmap) back in. If you don't you destroy the DC but your HBITMAP still thinks it is selected and so can't be selected into a new DC on the next draw. Thus your SelectObject fails.
Quote:
// Use IPicture stuff to use JPG / GIF files
My quess as Colin suggests (but I'll put a finer point on it) is that this code works ONCE on the first draw but it gets redrawn so fast that the bug you have in your code isn't obvious.
When you SelectObject(MemDc, myBitmap) you need to store the returned HBITMAP. Then after you are done with BitBlt() SelectObject(MemDc, oldBitmap) back in. If you don't you destroy the DC but your HBITMAP still thinks it is selected and so can't be selected into a new DC on the next draw. Thus your SelectObject fails.
...HBITMAP oldBitmap; // Somewhere to store the old HBITMAP...oldBitmap = (HBITMAP)SelectObject(MemDC, myBitmap); // Store the old HBITMAPBitBlt(myDC, 0, 0, iWidth, iHeight, MemDC, 0, 0, SRCCOPY);SelectObject(MemDc, oldBitmap); // Restore the old HBITMAP and free myBitmap...
Author
ok so this is what i have now
(myDC is a member variable of my Window class. i get myDC in the next source code, dont know if this will help my problem)
thank you everyone for showing interest in my problem
HDC MemDC = NULL; HBITMAP oldBitmap = NULL; PAINTSTRUCT Ps; //check any available messages from the queue switch (message) { case WM_PAINT: myDC = BeginPaint(myHwnd, &Ps); MemDC = CreateCompatibleDC(myDC); oldBitmap = (HBITMAP)SelectObject(MemDC, myBitmap); BitBlt(myDC, 0, 0, iWidth, iHeight, MemDC, 0, 0, SRCCOPY); SelectObject(MemDC, oldBitmap); DeleteDC(MemDC); EndPaint(myHwnd, &Ps); break;(myDC is a member variable of my Window class. i get myDC in the next source code, dont know if this will help my problem)
//create the Window from the class above myHwnd = CreateWindowEx(myWinExStyle, myWndClass.lpszClassName, myWndClass.lpszClassName, myWinStyle, (cen.right - myWidth) / 2, (cen.bottom - myHeight) / 2, rect.right - rect.left, rect.bottom - rect.top, NULL, NULL, this->myInst, this); if (!myHwnd) return false; myDC = GetDC(myHwnd);thank you everyone for showing interest in my problem
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