用WinAPI实现一个图片查看器：一个打开按钮，点击后打开一个打开文件对话框，打开选中的png文件显示在屏幕上，并可以用鼠标滚轮调整大小，并添加多彩画笔编辑功能，编辑完后点击保存按钮用保存文件对话框保存为png

好的，根据您的要求，我将为您提供一个基本的实现框架。以下是一个使用WinAPI实现图片查看器的示例代码：

#include <windows.h>
#include <commctrl.h>
#include <gdiplus.h>
#pragma comment(lib, "comctl32.lib")
#pragma comment(lib, "gdiplus.lib")

// 全局变量
HWND g_hWnd;
HWND g_hButtonOpen;
HWND g_hButtonSave;
HWND g_hImage;
HBITMAP g_hBitmap;
HPEN g_hPen;

// 函数声明
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
void OpenFile();
void SaveFile();
void Draw(HWND hWnd, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 初始化公共控件
    INITCOMMONCONTROLSEX icex;
    icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
    icex.dwICC = ICC_WIN95_CLASSES;
    InitCommonControlsEx(&icex);

    // 初始化GDI+
    Gdiplus::GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
    Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

    // 创建主窗口
    HWND hWnd;
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = hInstance;
    wcex.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = L"ImageViewer";
    wcex.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    RegisterClassEx(&wcex);

    g_hWnd = hWnd = CreateWindowEx(0, L"ImageViewer", L"图片查看器", WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL);

    // 创建打开按钮
    g_hButtonOpen = CreateWindowEx(0, L"BUTTON", L"打开", WS_CHILD | WS_VISIBLE,
        10, 10, 80, 30, hWnd, NULL, hInstance, NULL);

    // 创建保存按钮
    g_hButtonSave = CreateWindowEx(0, L"BUTTON", L"保存", WS_CHILD | WS_VISIBLE,
        100, 10, 80, 30, hWnd, NULL, hInstance, NULL);
    EnableWindow(g_hButtonSave, FALSE);

    // 创建显示图片的静态控件
    g_hImage = CreateWindowEx(0, L"STATIC", NULL, WS_CHILD | WS_VISIBLE | SS_BITMAP,
        10, 50, 780, 540, hWnd, NULL, hInstance, NULL);

    // 显示窗口
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    // 消息循环
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    // 释放GDI+
    Gdiplus::GdiplusShutdown(gdiplusToken);

    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_COMMAND:
        if (LOWORD(wParam) == (WORD)g_hButtonOpen)
        {
            OpenFile();
        }
        else if (LOWORD(wParam) == (WORD)g_hButtonSave)
        {
            SaveFile();
        }
        break;

    case WM_MOUSEWHEEL:
        if (g_hBitmap != NULL)
        {
            short zDelta = GET_WHEEL_DELTA_WPARAM(wParam);
            int width, height;
            GetClientRect(g_hImage, NULL);
            width = LOWORD(lParam);
            height = HIWORD(lParam);

            if (zDelta > 0) // 向上滚动
            {
                width += 10;
                height += 10;
            }
            else // 向下滚动
            {
                width -= 10;
                height -= 10;
            }

            SetWindowPos(g_hImage, NULL, 0, 0, width, height, SWP_NOMOVE | SWP_NOZORDER);
        }
        break;

    case WM_LBUTTONDOWN:
    case WM_MOUSEMOVE:
        if (g_hBitmap != NULL)
        {
            Draw(hWnd, lParam);
        }
        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    default:
        return DefWindowProc(hWnd, msg, wParam, lParam);
    }

    return 0;
}

void OpenFile()
{
    OPENFILENAME ofn;
    wchar_t szFile[MAX_PATH] = { 0 };
    ZeroMemory(&ofn, sizeof(ofn));

    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = g_hWnd;
    ofn.lpstrFile = szFile;
    ofn.nMaxFile = sizeof(szFile);
    ofn.lpstrFilter = L"PNG文件\0*.png\0";
    ofn.nFilterIndex = 1;
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;

    if (GetOpenFileName(&ofn))
    {
        Gdiplus::Bitmap* bitmap = new Gdiplus::Bitmap(szFile);
        if (bitmap->GetLastStatus() == Gdiplus::Ok)
        {
            if (g_hBitmap != NULL)
            {
                DeleteObject(g_hBitmap);
            }
            g_hBitmap = (HBITMAP)bitmap->GetHBITMAP();

            SendMessage(g_hImage, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)g_hBitmap);

            EnableWindow(g_hButtonSave, TRUE);
        }

        delete bitmap;
    }
}

void SaveFile()
{
    OPENFILENAME ofn;
    wchar_t szFile[MAX_PATH] = { 0 };
    ZeroMemory(&ofn, sizeof(ofn));

    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = g_hWnd;
    ofn.lpstrFile = szFile;
    ofn.nMaxFile = sizeof(szFile);
    ofn.lpstrFilter = L"PNG文件\0*.png\0";
    ofn.nFilterIndex = 1;
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_OVERWRITEPROMPT;

    if (GetSaveFileName(&ofn))
    {
        Gdiplus::Bitmap* bitmap = new Gdiplus::Bitmap(g_hBitmap, NULL);
        if (bitmap->GetLastStatus() == Gdiplus::Ok)
        {
            bitmap->Save(szFile, &Gdiplus::ImageFormatPNG);
        }

        delete bitmap;
    }
}

void Draw(HWND hWnd, LPARAM lParam)
{
    HDC hdc = GetDC(hWnd);

    int x = LOWORD(lParam);
    int y = HIWORD(lParam);

    if (GetAsyncKeyState(VK_LBUTTON) & 0x8000)
    {
        if (g_hPen == NULL)
        {
            g_hPen = CreatePen(PS_SOLID, 5, RGB(255, 0, 0));
        }
        SelectObject(hdc, g_hPen);
        MoveToEx(hdc, x, y, NULL);
        LineTo(hdc, x, y);
    }

    ReleaseDC(hWnd, hdc);
}

请注意，上述代码仅提供了一个基本的框架，您可能需要根据自己的需求进行修改和完善。此示例使用了GDI+库来加载和保存图片，并使用GDI函数进行绘制。在编译时，请确保已添加所需的库文件并设置好编译器的附加包含目录。

希望这可以帮助到您！如果您有任何更多问题，请随时提问。