C++ GDI实现图片格式转换

#include <windows.h>
#include <gdiplus.h>
 
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
 
int main()
{
    // 初始化GDI+
    Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
    
    // 进行图像处理操作
    
    // 关闭GDI+
    Gdiplus::GdiplusShutdown(gdiplusToken);
    
    return 0;
}

Gdiplus::Bitmap* sourceImage = Gdiplus::Bitmap::FromFile(L"input.jpg");

Gdiplus::Bitmap* targetImage = new Gdiplus::Bitmap(sourceImage->GetWidth(), sourceImage->GetHeight(), sourceImage->GetPixelFormat());

Gdiplus::Graphics graphics(targetImage);
graphics.DrawImage(sourceImage, 0, 0, sourceImage->GetWidth(), sourceImage->GetHeight());

targetImage->Save(L"output.png", Gdiplus::ImageFormatPNG);

delete sourceImage;
delete targetImage;

#include <windows.h>
#include <gdiplus.h>
#include <stdio.h>
#include <string>
using namespace Gdiplus;
 
#pragma comment(lib,"gdiplus")
 
int GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
    UINT num = 0; // number of image encoders
    UINT size = 0; // size of the image encoder array in bytes
 
    ImageCodecInfo* pImageCodecInfo = NULL;
 
    // Get the number of image encoders and the size of the array
    GetImageEncodersSize(&num, &size);
    if (size == 0)
        return -1;  // Failure
 
    // Allocate memory for the image encoder array
    pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
    if (pImageCodecInfo == NULL)
        return -1;  // Failure
 
    // Get all image encoders
    GetImageEncoders(num, size, pImageCodecInfo);
 
    // Find the image encoder that matches the specified format
    for (UINT j = 0; j < num; ++j)
    {
        if (wcscmp(pImageCodecInfo[j].MimeType, format) == 0)
        {
            *pClsid = pImageCodecInfo[j].Clsid;
            free(pImageCodecInfo);
            return j;  // Success
        }
    }
 
    // Free the allocated memory
    free(pImageCodecInfo);
    return -1;  // Failure
}
 
bool ConvertImageFormatFromMemory(const char* imageData, ULONG imageDataSize, const std::string& outputFilePath, const wchar_t* outputFormat)
{
    GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
 
    // Initialize GDI+
    GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
 
    CLSID encoderClsid;
    Status stat;
 
    // Create a stream from the image data
    IStream* pStream = NULL;
    CreateStreamOnHGlobal(NULL, TRUE, &pStream);
    pStream->Write(imageData, imageDataSize, NULL);
    pStream->Seek({ 0 }, STREAM_SEEK_SET, NULL);
 
    // Load the image from the stream
    Bitmap* bitmap = new Bitmap(pStream, FALSE);
    Image* image = static_cast<Image*>(bitmap);
 
    // Get the CLSID of the output format encoder
    GetEncoderClsid(outputFormat, &encoderClsid);
 
    // Convert the output file path to wide-character string
    int wideCharLen = MultiByteToWideChar(CP_UTF8, 0, outputFilePath.c_str(), -1, NULL, 0);
    wchar_t* wideCharPath = new wchar_t[wideCharLen];
    MultiByteToWideChar(CP_UTF8, 0, outputFilePath.c_str(), -1, wideCharPath, wideCharLen);
 
    // Save the image in the desired format
    stat = image->Save(wideCharPath, &encoderClsid, NULL);
 
    // Clean up
    delete image;
    pStream->Release();
    GdiplusShutdown(gdiplusToken);
    delete[] wideCharPath;
 
    return (stat == Ok);
}
 
int main()
{
    // Assuming you have the BMP image data in a `char*` buffer named `imageData`
    char* imageData = /* Your BMP image data */;
    ULONG imageDataSize = /* Size of the BMP image data */;
 
    const std::string outputFilePath = "output.jpg";
    const wchar_t* outputFormat = L"image/jpeg";
 
    bool success = ConvertImageFormatFromMemory(imageData, imageDataSize, outputFilePath, outputFormat);
 
    if (success)
        printf("Image saved successfully.\n");
    else
        printf("Failed to save image.\n");
 
    return 0;
}