C ++从hBitmap获取RGB [英] C++ Getting RGB from hBitmap

问题描述

使用位图对我来说是非常陌生的，所以我一直在努力阅读已读过的在线教程和策略.基本上，我的目标是扫描屏幕上的特定RGB值.我相信要执行此操作的步骤是在hBitmap中捕获屏幕，然后从中生成可以扫描的RGB值数组.

Working with bitmaps is very new to me so I've been really struggling with the online tutorials and strategies that I've read through. Basically my goal is to scan the screen for a particular RGB value. I believe the steps to do this is to capture the screen in a hBitmap and then produce an array of RGB values from it that I can scan through.

我最初是从GetPixel开始的，但是那太慢了.解决方案是使用GetDIBits来生成RGB值的数组.问题在于它返回的是奇怪的RGB值，而且可能是随机的.

I originally started with GetPixel but that is very slow. The solution was to use GetDIBits which produces the array of RGB values. The problem is that it returns weird and possibly random RGB values instead.

我正在使用从另一个教程中找到的以下代码:

I'm using the following code which I found from another tutorial:

/* Globals */
int ScreenX = GetDeviceCaps(GetDC(0), HORZRES);
int ScreenY = GetDeviceCaps(GetDC(0), VERTRES);
BYTE* ScreenData = new BYTE[3*ScreenX*ScreenY];

void ScreenCap() {
    HDC hdc = GetDC(GetDesktopWindow());
    HDC hdcMem = CreateCompatibleDC (hdc);
    HBITMAP hBitmap = CreateCompatibleBitmap(hdc, ScreenX, ScreenY);
    BITMAPINFOHEADER bmi = {0};
    bmi.biSize = sizeof(BITMAPINFOHEADER);
    bmi.biPlanes = 1;
    bmi.biBitCount = 24;
    bmi.biWidth = ScreenX;
    bmi.biHeight = -ScreenY;
    bmi.biCompression = BI_RGB;
    bmi.biSizeImage = ScreenX * ScreenY;
    SelectObject(hdcMem, hBitmap);
    BitBlt(hdcMem, 0, 0, ScreenX, ScreenY, hdc, 0, 0, SRCCOPY);
    GetDIBits(hdc, hBitmap, 0, ScreenY, ScreenData, (BITMAPINFO*)&bmi, DIB_RGB_COLORS);

    DeleteDC(hdcMem);
    ReleaseDC(NULL, hdc);
}

inline int PosR(int x, int y) {
    return ScreenData[3*((y*ScreenX)+x)+2];
}

inline int PosG(int x, int y) {
    return ScreenData[3*((y*ScreenX)+x)+1];
}

inline int PosB(int x, int y) {
    return ScreenData[3*((y*ScreenX)+x)];
}

我用以下代码对此进行测试.我按下Shift键调用ScreenCap，然后将光标移动到所需位置，然后按下Space键以查看该位置的RGB值.我完全疯了吗?

I test this with the following code. I hit Shift to call ScreenCap and then I move my cursor to the desired location and hit Space to see what the RGB value is at that location. Am I completely nuts?

int main() {

while ( true ) {

   if (GetAsyncKeyState(VK_SPACE)){  

      // Print out current cursor position
      GetCursorPos(&p);
      printf("X:%d Y:%d \n",p.x,p.y);
      // Print out RGB value at that position
      int r = PosR(p.x, p.y);
      int g = PosG(p.x, p.y);
      int b = PosB(p.x, p.y);
      printf("r:%d g:%d b:%d \n",r,g,b);

   } else if (GetAsyncKeyState(VK_ESCAPE)){
      printf("Quit\n");
      break;
   } else if (GetAsyncKeyState(VK_SHIFT)){
      ScreenCap();
      printf("Captured\n");
   }
}

system("PAUSE");
return 0;
}

推荐答案

问题是您的屏幕实际上是32位深而不是24位.下面的代码将为您提供所需的结果:

The issue is that your screen is actually 32bits deep not 24. The code below will give you the result you need:

/* Globals */
int ScreenX = 0;
int ScreenY = 0;
BYTE* ScreenData = 0;

void ScreenCap() 
{
    HDC hScreen = GetDC(NULL);
    ScreenX = GetDeviceCaps(hScreen, HORZRES);
    ScreenY = GetDeviceCaps(hScreen, VERTRES);

    HDC hdcMem = CreateCompatibleDC(hScreen);
    HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, ScreenX, ScreenY);
    HGDIOBJ hOld = SelectObject(hdcMem, hBitmap);
    BitBlt(hdcMem, 0, 0, ScreenX, ScreenY, hScreen, 0, 0, SRCCOPY);
    SelectObject(hdcMem, hOld);

    BITMAPINFOHEADER bmi = {0};
    bmi.biSize = sizeof(BITMAPINFOHEADER);
    bmi.biPlanes = 1;
    bmi.biBitCount = 32;
    bmi.biWidth = ScreenX;
    bmi.biHeight = -ScreenY;
    bmi.biCompression = BI_RGB;
    bmi.biSizeImage = 0;// 3 * ScreenX * ScreenY;

    if(ScreenData)
        free(ScreenData);
    ScreenData = (BYTE*)malloc(4 * ScreenX * ScreenY);

    GetDIBits(hdcMem, hBitmap, 0, ScreenY, ScreenData, (BITMAPINFO*)&bmi, DIB_RGB_COLORS);

    ReleaseDC(GetDesktopWindow(),hScreen);
    DeleteDC(hdcMem);
    DeleteObject(hBitmap);
}

inline int PosB(int x, int y) 
{
    return ScreenData[4*((y*ScreenX)+x)];
}

inline int PosG(int x, int y) 
{
    return ScreenData[4*((y*ScreenX)+x)+1];
}

inline int PosR(int x, int y) 
{
    return ScreenData[4*((y*ScreenX)+x)+2];
}

bool ButtonPress(int Key)
{
    bool button_pressed = false;

    while(GetAsyncKeyState(Key))
        button_pressed = true;

    return button_pressed;
}

int main() 
{
    while (true) 
    {
       if (ButtonPress(VK_SPACE))
       {  

          // Print out current cursor position
          POINT p;
          GetCursorPos(&p);
          printf("X:%d Y:%d \n",p.x,p.y);
          // Print out RGB value at that position
          std::cout << "Bitmap: r: " << PosR(p.x, p.y) << " g: " << PosG(p.x, p.y) << " b: " << PosB(p.x, p.y) << "\n";

       } else if (ButtonPress(VK_ESCAPE))
       {
          printf("Quit\n");
          break;
       } else if (ButtonPress(VK_SHIFT))
       {
          ScreenCap();
          printf("Captured\n");
       }
    }

    system("PAUSE");
    return 0;
}

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