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c - 数组缓冲区和winapi

问题描述

语境 ：

问题 ：

我有一个像素缓冲区，表示uint8_t buffer[width * height * PIXEL_SIZE]我想定期修改内容数据并将缓冲区重绘到窗口中。

我遇到了两个与我迷路的winapi有关的问题：

我做了很多研究，但没有代码片段成功地帮助我解决了我的问题。

这是一个不工作的代码示例，以显示我想用我拥有的代码元素归档的内容：

new_image.c

// Global variables
static HDC      hdc;
static HDC      context_hdc;
static HBITMAP  hDib;
static HGDIOBJ  obj;

static void     set_bmi_object(BITMAPINFO *bmi, int width, int height) {
    memset(bmi, 0, sizeof(BITMAPINFO));

    bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi->bmiHeader.biWidth = width;
    bmi->bmiHeader.biHeight = -height;
    bmi->bmiHeader.biPlanes = 1;
    bmi->bmiHeader.biBitCount = 32;
    bmi->bmiHeader.biCompression = BI_RGB;
}

// Allocate a new image buffer
void             *new_image(HWND hwnd, int width, int height)
{
    BITMAPINFO  bmi;
    BYTE        *bits = NULL;
    void        *buffer;

    if (NULL == (buffer = (char*)malloc(width * height * PIXEL_SIZE)))
        return (NULL);

    set_bmi_object(&bmi, width, height);

    hdc = GetDC(hwnd);

    hDib = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, (void**)(&bits), 
                            NULL, 0);

    if (hDib != NULL) {
        context_hdc = CreateCompatibleDC(hdc);
        if (context_hdc == NULL) {
            DeleteObject(hDib);
        } else {
            obj = SelectObject(context_hdc, hDib);
            CopyMemory(bits, buffer, width * height * sizeof(PIXEL_SIZE));
        }
    }

    return (newimg);
}

// Print the buffer of pixel on the window
void             put_image_to_window(HWND hwnd, void *buffer, int x, int y)
{
    (void)hwnd;

    // Void buffer because i should use directly HDCcontext_hdc linked to HGDIOBJ   obj ?
    (void)buffer;

    BitBlt(hdc, // destination
        x,
        y,
        500, // width of the region
        500, // height
        context_hdc, // source
        0,   // x
        0,   // y
        SRCCOPY);

    UpdateWindow(hwnd);
}

主程序

static const char g_szClassName[] = "myWindowClass";

static void paint(HWND hwnd) {
    PAINTSTRUCT ps;
    HDC hdc = BeginPaint(hwnd, &ps);
    EndPaint(hwnd, &ps);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    case WM_PAINT:
        paint(hwnd);
    return DefWindowProc(hwnd, msg, wParam, lParam);
}

int main(void) {
    MSG             Msg;
    HINSTANCE       hInstance;
    HWND            hwnd;
    STARTUPINFOA    startup_info;
    WNDCLASSEX      wc;
    HWND            hwnd;

    GetStartupInfoA(&startup_info);

    hInstance = GetModuleHandle(NULL);

    memset(&wc, 0, sizeof(wc));

    // Registering the Window Class
    wc.cbSize = sizeof(WNDCLASSEX);
    // ... etc
    wc.lpszClassName = TEXT(g_szClassName);

    if (!RegisterClassEx(&wc)) {
        return (-1);
    }

    hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        g_szClassName,
        "Title,
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        500, 
        500,
        NULL,
        NULL,
        hInstance,
        NULL);

    if (hwnd == NULL) {
        return (-1);
    }

    ShowWindow(hwnd, startup_info.wShowWindow);


    image = new_image(hwnd, 500, 500);

    put_image_to_window(hwnd, image, 0, 0);

    UpdateWindow(hwnd);

    // The Message Loop
    while (GetMessage(&Msg, NULL, 0, 0)) {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }

    return (Msg.wParam);
}

这是在new_image.c

标签： cwindowswinapipixmap

解决方案

CopyMemory(bits, buffer, width * height * sizeof(PIXEL_SIZE));

运算符的使用sizeof不正确。位图可以是 1、4、8、16、24 或 32 位。32 位位图每个像素有 4 个字节。如果PIXEL_SIZE被声明为int32_t那么巧合你得到正确的大小。否则使用正确的公式来计算大小。

此外，复制buffer到bits. 你可以bits直接使用。bits只要你没有销毁就有效hDib

hdc = GetDC(hwnd);

调用GetDC应该以 结束ReleaseDC，否则你可能会导致资源泄漏。Windows 设备上下文并不意味着存储为常量。将其用作临时值。

您还声明HDC context_hdc为全局变量。这对于内存设备上下文是可以的，但这不是必需的。您需要的唯一全局变量hDib可能是buffer

#include <windows.h>

static const char g_szClassName[] = "myWindowClass";
static HBITMAP  hDib;

BYTE *new_image(int width, int height)
{
    BITMAPINFO bmi;
    memset(&bmi, 0, sizeof(BITMAPINFO));
    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi.bmiHeader.biWidth = width;
    bmi.bmiHeader.biHeight = -height;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = BI_RGB;

    BYTE *buffer;
    HDC hdc = GetDC(HWND_DESKTOP);
    hDib = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, (void**)(&buffer), NULL, 0);
    ReleaseDC(HWND_DESKTOP, hdc);
    return buffer;
}

static void paint(HWND hwnd) 
{
    PAINTSTRUCT ps;
    HDC hdc = BeginPaint(hwnd, &ps);

    if(hDib)
    {
        HDC context_hdc = CreateCompatibleDC(hdc);
        HGDIOBJ old_obj = SelectObject(context_hdc, hDib);
        BitBlt(hdc, 0, 0, 500, 500, context_hdc, 0, 0, SRCCOPY);
        SelectObject(context_hdc, old_obj);
        DeleteDC(context_hdc);
    }

    EndPaint(hwnd, &ps);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    case WM_PAINT:
        paint(hwnd);
        break;
    case WM_MOUSEMOVE:
    {
        if(hDib)
        {
            //draw something
            HDC context_hdc = CreateCompatibleDC(NULL);
            HGDIOBJ old_obj = SelectObject(context_hdc, hDib);

            SetDCBrushColor(context_hdc, RGB(255, 0, 0));
            int x = (int)(short)LOWORD(lParam);
            int y = (int)(short)HIWORD(lParam);
            RECT rc = { x, y, x + 10, y + 10};
            FillRect(context_hdc, &rc, (HBRUSH)GetStockObject(DC_BRUSH));

            SelectObject(context_hdc, old_obj);
            DeleteDC(context_hdc);

            InvalidateRect(hwnd, NULL, FALSE);
        }
        break;
    }
    }
    return DefWindowProc(hwnd, msg, wParam, lParam);
}

int main(void) {
    MSG             Msg;
    HINSTANCE       hInstance;
    HWND            hwnd;
    STARTUPINFOA    startup_info;
    WNDCLASSEX      wc;

    GetStartupInfoA(&startup_info);
    hInstance = GetModuleHandle(NULL);
    memset(&wc, 0, sizeof(wc));
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszClassName = TEXT(g_szClassName);
    RegisterClassEx(&wc);

    hwnd = CreateWindowEx(WS_EX_CLIENTEDGE, g_szClassName, "Title",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        CW_USEDEFAULT, CW_USEDEFAULT,
        500, 500, NULL, NULL, hInstance, NULL);

    BYTE* image = new_image(500, 500);

    ShowWindow(hwnd, SW_SHOW);//startup_info.wShowWindow);
    UpdateWindow(hwnd);
    while(GetMessage(&Msg, NULL, 0, 0)) 
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }

    if (hDib)
        DeleteObject(hDib);

    return (Msg.wParam);
}

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