How to draw bitmap data in memory on DC

Explain in detail how to draw bitmap data in memory in the device context (DC):

In Windows programming, we can use GDI (Graphic Device Interface) to draw Bitmap data in memory is drawn on the device context (DC). The following are some steps and sample code:

1. Puzzle solving steps:

1. 1. Create a bitmap in memory: Use the CreateCompatibleBitmap function to create a compatible bitmap, then use the CreateCompatibleDC function to create a compatible memory DC and select the bitmap into the memory DC.

2. 2. Draw the image to the bitmap: Use GDI functions, such as SelectObject and BitBlt, to draw the image data onto the bitmap.

3. 3. Draw the bitmap in memory to the screen DC: Use the BitBlt function to draw the bitmap in memory to the target DC (usually the window's DC).

2. The sample code is as follows:

#include <Windows.h>

void DrawBitmapOnDC(HDC hdc, HBITMAP hBitmap, int x, int y) {
    // 创建内存DC
    HDC memDC = CreateCompatibleDC(hdc);

    // 选择位图到内存DC
    HBITMAP oldBitmap = (HBITMAP)SelectObject(memDC, hBitmap);

    // 获取位图信息
    BITMAP bitmapInfo;
    GetObject(hBitmap, sizeof(BITMAP), &bitmapInfo);

    // 将内存中的位图绘制到屏幕DC
    BitBlt(hdc, x, y, bitmapInfo.bmWidth, bitmapInfo.bmHeight, memDC, 0, 0, SRCCOPY);

    // 恢复原始位图
    SelectObject(memDC, oldBitmap);

    // 删除内存DC
    DeleteDC(memDC);
}

int main() {
    // 获取窗口DC
    HWND hWnd = GetDesktopWindow();
    HDC hdc = GetDC(hWnd);

    // 创建内存中的位图
    HBITMAP hBitmap = CreateCompatibleBitmap(hdc, 100, 100);

    // 绘制图像到位图
    // 这里可以使用其他方式加载图像数据到位图，例如LoadImage、GDI+等
    // 为示例，这里创建一个红色的位图
    HBRUSH hBrush = CreateSolidBrush(RGB(255, 0, 0));
    HDC memDC = CreateCompatibleDC(hdc);
    HBITMAP oldBitmap = (HBITMAP)SelectObject(memDC, hBitmap);
    FillRect(memDC, &RECT{ 0, 0, 100, 100 }, hBrush);
    SelectObject(memDC, oldBitmap);
    DeleteDC(memDC);
    DeleteObject(hBrush);

    // 将内存中的位图绘制到窗口DC
    DrawBitmapOnDC(hdc, hBitmap, 100, 100);

    // 释放资源
    DeleteObject(hBitmap);
    ReleaseDC(hWnd, hdc);

    return 0;
}

Summary:

To be drawn on DC For bitmap data in memory, you first need to create a compatible bitmap and memory DC, then use GDI functions to draw the image onto the bitmap, and finally draw the bitmap onto the target DC. This process includes the steps of creating a bitmap, drawing it, and drawing it to the screen.

The above is the detailed content of How to draw bitmap data in memory on DC. For more information, please follow other related articles on the PHP Chinese website!