Load bitmap using GDI+ in C

bitmap.c

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

Bitmap* loadBitmap(char* file)
{
    int length = strlen(file) + 1;

    wchar_t* fileW = (wchar_t*) malloc(length * sizeof(wchar_t));

    if (!fileW)
        die("Unable to allocate wide string");

    if (mbstowcs(fileW, file, length) == -1)
        die("Unable to create wide string");

    GpBitmap* gpBitmap;

    if (GdipCreateBitmapFromFile(fileW, &gpBitmap) != Ok)
        die("Unable to create bitmap");

    int width;
    int height;

    if (GdipGetImageWidth(gpBitmap, &width) != Ok || GdipGetImageHeight(gpBitmap, &height) != Ok)
        die("Unable to get bitmap dimension");

    char* bytes = malloc(width * height * 4);

    if (!bytes)
        die("Unable to allocate bytes");

    BitmapData data = { .Scan0 = bytes, .Stride = width * 4 };
    GpRect     rect = { .Width = width, .Height = height };

    if (GdipBitmapLockBits(gpBitmap, &rect, ImageLockModeRead | ImageLockModeUserInputBuf, PixelFormat32bppARGB, &data) != Ok)
        die("Unable to lock bitmap");

    Bitmap* bitmap = (Bitmap*) malloc(sizeof(Bitmap));

    if (!bitmap)
        die("Unable to allocate bitmap");

    bitmap->bytes  = bytes;
    bitmap->width  = width;
    bitmap->height = height;

    GdipDisposeImage(gpBitmap);
    free(fileW);

    return bitmap;
}

// Need some initialization

ULONG_PTR token;
GdiplusStartupInput input = { .GdiplusVersion = 1 };
GdiplusStartup(&token, &input, 0);