Understanding how to display an image

Question

I'm attempting to understand how to display an image onto a window using the code from "Loading and displaying bitmaps"

Image image(L"Grapes.jpg");

graphics.DrawImage(&image, 60, 10);

I have been able to get the first line working by including gdiplusheaders.h , but I haven't found a way to fix "graphics unidentified". I attempted to use the AI helper, but it claims it couldn't find headers for it. Any help to solving or explaining how the two lines work is appreciated.

Answer 1

Thank you @Tong Xu - MSFT , but the code you provided only created a black window regardless if I changed the path to an image. However your code gave me ideas on how to rephrase my question and the AI posted this. I must also emphasize that I am still learning Win32 and am not knowledgeable in all terminology, headers, classes etc.

#include <windows.h>
#include <gdiplus.h>

using namespace Gdiplus;
//Next line was missing
#pragma comment(lib, "gdiplus.lib")

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            Graphics graphics(hdc);
            Image image(L"C:\\path\\to\\image.jpg");
            graphics.DrawImage(&image, 0, 0);
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
        break;
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
    GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

    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(hInstance, IDI_APPLICATION);
    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = L"WindowClass";
    wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);

    if (!RegisterClassEx(&wcex))
    {
        MessageBox(NULL, L"Window Registration Failed!", L"Error!", MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    HWND hWnd = CreateWindowEx(WS_EX_CLIENTEDGE, L"WindowClass", L"Window Title", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 640, 480, NULL, NULL, hInstance, NULL);

    if (hWnd == NULL)
    {
        MessageBox(NULL, L"Window Creation Failed!", L"Error!", MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    GdiplusShutdown(gdiplusToken);
    return msg.wParam;
}

As far as I understand you will need to include gdiplus.h, using namespace gdiplus, and #pragma comment (lib, "gdiplus.lib") or linking to the library itself. That will allow it to access code it needs for the Image and Graphics classes under GDI+. Then before creating the window, you must initialize GDI+ then shutdown GDI+ at the end (which I'm assuming is to free up resources.). It produces the image when given a path to one, but will allow the window to stretch up to the image's size.

Answer 2

Hi, @Willard
Welcome to Microsoft Q&A!

I remember graphics.DrawImage used 5 parameters. Your usage is wrong.
When "graphics unidentified" occurred, you should add namespace and library.
using namespace Gdiplus;
#pragma comment(lib,"gdiplus.lib")

Also, I made a code sample to show how to use GDI+ to show images.

#ifndef UNICODE
#define UNICODE
#endif 
#include <windows.h>
#include <gdiplus.h>
using namespace Gdiplus;
#pragma comment(lib,"gdiplus.lib")
ULONG_PTR gdiplusStartupToken;
Gdiplus::GdiplusStartupInput gdiInput;
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)
{
    // Register the window class.
    const wchar_t CLASS_NAME[] = L"Sample Window Class";
    WNDCLASSEX wincl = { };
    wincl.hInstance = hInstance;
    wincl.lpszClassName = CLASS_NAME;
    wincl.lpfnWndProc = WindowProc;
    wincl.style = CS_DBLCLKS;
    wincl.cbSize = sizeof(WNDCLASSEX);
    wincl.hIcon = NULL;
    wincl.hIconSm = NULL;
    wincl.hCursor = NULL;
    wincl.lpszMenuName = NULL;
    wincl.cbClsExtra = 0;
    wincl.cbWndExtra = 0;
    wincl.hbrBackground = (HBRUSH)COLOR_BACKGROUND;
    RegisterClassEx(&wincl);
    // Create the window.
    HWND hwnd = CreateWindowEx(
        WS_EX_LAYERED ,
        (LPCWSTR)CLASS_NAME,
        L"PNGDialog Example Application",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        500,
        500,
        0,
        NULL,
        hInstance,
        NULL
    );
    RECT wndRect;
    SIZE wndSize;
    HDC hdc;
    POINT ptSrc;
    BLENDFUNCTION blendFunction;
    HDC screenDC;
    HDC memDC;
    HBITMAP memBitmap;
    GetWindowRect(hwnd, &wndRect);
    wndSize = { wndRect.right - wndRect.left,wndRect.bottom - wndRect.top };
    hdc = GetDC(hwnd);
    memDC = CreateCompatibleDC(hdc);
    memBitmap = ::CreateCompatibleBitmap(hdc, wndSize.cx, wndSize.cy);
    ::SelectObject(memDC, memBitmap);
    Gdiplus::Image image(L"001.bmp");
    Gdiplus::Graphics graphics(memDC);
    graphics.DrawImage(&image, 0, 0, wndSize.cx, wndSize.cy);
    // Run the message loop.
    screenDC = GetDC(NULL);
    ptSrc = { 0,0 };
    UpdateLayeredWindow(hwnd, screenDC, &ptSrc, &wndSize, memDC, &ptSrc, 0, &blendFunction, 4);
    ShowWindow(hwnd, SW_SHOW);
    UpdateWindow(hwnd);
  
    MSG msg = { };
    while (GetMessage(&msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    Gdiplus::GdiplusStartup(&gdiplusStartupToken, &gdiInput, NULL);
    switch (uMsg)
    {
    case WM_DESTROY:
        Gdiplus::GdiplusShutdown(gdiplusStartupToken);
        PostQuitMessage(0);
        return 0;
    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        SIZE wndSize;
        HBITMAP memBitmap;
        HDC memDC;
        HDC hdc = BeginPaint(hwnd, &ps);
       
        // All painting occurs here, between BeginPaint and EndPaint.
        FillRect(hdc, &ps.rcPaint, (HBRUSH)(COLOR_WINDOW + 1));
        EndPaint(hwnd, &ps);
    }
    return 0;
    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}  

Thank you.

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