Function LoadPicture

Source/util.cpp:1172–1466

HBITMAP LoadPicture(char *aFilespec, int aWidth, int aHeight, int &aImageType, int aIconIndex, bool aUseGDIPlusIfAvailable)
// Loads a JPG/GIF/BMP/ICO/etc. and returns an HBITMAP or HICON to the caller (which it may call
// DeleteObject()/DestroyIcon() upon, though upon program termination all such handles are freed
// automatically).  The image is scaled to the specified width and height.  If zero is specified
// for either, the image's actual size will be used for that dimension.  If -1 is specified for one,
// that dimension will be kept proportional to the other dimension's size so that the original aspect
// ratio is retained.  Caller should specify -1 for aIconIndex unless an icon other than 1 is desired.
// .ico/.cur/.ani files are normally loaded as HICON (unless aUseGDIPlusIfAvailable is true of something
// else unusual happened such as file contents not matching file's extension).  This is done to preserve
// any properties that HICONs have but HBITMAPs lack, namely the ability to be animated and perhaps other things.
// Returns NULL on failure.
{
	HBITMAP hbitmap = NULL;
	aImageType = -1; // The type of image currently inside hbitmap.  Set default value for output parameter as "unknown".

	char *file_ext = strrchr(aFilespec, '.');
	if (file_ext)
		++file_ext;

	// Must use ExtractIcon() if either of the following is true:
	// 1) Caller gave an explicit icon index, i.e. it wants us to use ExtractIcon() even for the first icon.
	// 2) The target file is an EXE or DLL (LoadImage() is documented not to work on those file types).
	bool ExtractIcon_was_used = aIconIndex >= 0 || (file_ext && (!stricmp(file_ext, "exe") || !stricmp(file_ext, "dll")));
	if (ExtractIcon_was_used)
	{
		aImageType = IMAGE_ICON;
		if (aIconIndex < 0)
			aIconIndex = 0;  // Use the default, which is the first icon.
		hbitmap = (HBITMAP)ExtractIcon(g_hInstance, aFilespec, aIconIndex); // Return value of 1 means "incorrect file type".
		if (!hbitmap || hbitmap == (HBITMAP)1 || (!aWidth && !aHeight)) // Couldn't load icon, or could but no resizing is needed.
			return hbitmap;
		//else continue on below so that the icon can be resized to the caller's specified dimensions.
	}

	// Make an initial guess of the type of image if the above didn't already determine the type:
	if (aImageType < 0)
	{
		if (file_ext) // Assume generic file-loading method if there's no file extension.
		{
			if (!stricmp(file_ext, "ico"))
				aImageType = IMAGE_ICON;
			else if (!stricmp(file_ext, "cur") || !stricmp(file_ext, "ani"))
				aImageType = IMAGE_CURSOR;
			else if (!stricmp(file_ext, "bmp"))
				aImageType = IMAGE_BITMAP;
			//else for other extensions, leave set to "unknown" so that the below knows to use IPic or GDI+ to load it.
		}
		//else same comment as above.
	}

	if ((aWidth == -1 || aHeight == -1) && (!aWidth || !aHeight))
		aWidth = aHeight = 0; // i.e. One dimension is zero and the other is -1, which resolves to the same as "keep original size".
	bool keep_aspect_ratio = (aWidth == -1 || aHeight == -1);

	HINSTANCE hinstGDI = NULL;
	if (aUseGDIPlusIfAvailable && !(hinstGDI = LoadLibrary("GdiPlus.dll")))
		aUseGDIPlusIfAvailable = false; // Override this value as a signal for the section below.