- 1 year ago
I cannot convert a GDI+ bitmap to base 64 in C++ (Microsoft Visual C++)
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To convert a GDI+ bitmap to base64 in C++ using Microsoft Visual C++, you can follow these steps:
Load and Encode Bitmap: Load the bitmap using GDI+ and encode it as a PNG or JPEG image into a memory stream. Here's an example:
cpp#include <gdiplus.h>
#include <atlenc.h> // for Base64Encode
std::string BitmapToBase64(Gdiplus::Bitmap* bitmap)
{
CLSID encoderClsid;
Gdiplus::Status status;
IStream* stream = nullptr;
// Create a memory stream for encoding the bitmap
if (CreateStreamOnHGlobal(nullptr, TRUE, &stream) != S_OK)
{
return "";
}
// Determine the encoder for the desired image format (PNG or JPEG)
if (bitmap->GetEncoderClsid((bitmap->GetImageFormat() == Gdiplus::ImageFormatPNG) ? L"image/png" : L"image/jpeg", &encoderClsid) != Gdiplus::Ok)
{
stream->Release();
return "";
}
// Save the bitmap to the memory stream
status = bitmap->Save(stream, &encoderClsid, nullptr);
// Get the size of the memory stream
LARGE_INTEGER liSize;
ULARGE_INTEGER liSeek;
liSeek.QuadPart = 0;
if (stream->Seek(liSeek, STREAM_SEEK_END, &liSize) != S_OK)
{
stream->Release();
return "";
}
// Rewind the memory stream to the beginning
liSeek.QuadPart = 0;
if (stream->Seek(liSeek, STREAM_SEEK_SET, nullptr) != S_OK)
{
stream->Release();
return "";
}
// Read the encoded image data from the memory stream
BYTE* data = new BYTE[liSize.LowPart];
ULONG bytesRead;
if (stream->Read(data, liSize.LowPart, &bytesRead) != S_OK)
{
delete[] data;
stream->Release();
return "";
}
// Encode the image data as base64
std::string base64Encoded;
base64Encoded = base64Encoded.Encode(data, bytesRead);
// Cleanup
delete[] data;
stream->Release();
return base64Encoded;
}
Usage Example: Here's an example of how you can use the
BitmapToBase64
function:cppint main()
{
// Initialize GDI+
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, nullptr);
// Load the bitmap from a file
Gdiplus::Bitmap* bitmap = new Gdiplus::Bitmap(L"image.bmp");
// Convert the bitmap to base64
std::string base64Data = BitmapToBase64(bitmap);
// Print the base64-encoded data
std::cout << base64Data << std::endl;
// Cleanup
delete bitmap;
Gdiplus::GdiplusShutdown(gdiplusToken);
return 0;
}
Ensure that you have included the necessary headers (<gdiplus.h>
and <atlenc.h>
) and linked against the GDI+ library in your Visual C++ project.
Remember to handle any potential error conditions, release resources properly, and adjust the code as needed based on your specific requirements.