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src/Source/FreeImage/PluginPCX.cpp  view on Meta::CPAN

	The Validate function is used by using FreeImage_GetFileType.
	
	Note: a plugin can safely read data any data from the bitmap without seeking back
	to the original entry point; the entry point is stored prior to calling this
	function and restored after.

    Note: because of FreeImage's io redirection support, the header for the bitmap
	must be on the start of the bitmap or at least on a known part in the bitmap. It is
	forbidden to seek to the end of the bitmap or to a point relative to the end of a bitmap,
	because the end of the bitmap is not always known.
*/

static BOOL DLL_CALLCONV
Validate(FreeImageIO *io, fi_handle handle) {
	return pcx_validate(io, handle);
}

/*!
    This function is used to 'ask' the plugin if it can write
	a bitmap in a certain bitdepth. Different bitmap types have different
	capabilities, for example not all formats allow writing in palettized mode.
	This function is there provide an uniform interface to the plugin's
	capabilities. SupportsExportDepth returns TRUE if the plugin support writing
	in the asked bitdepth, or FALSE if it doesn't. The function also
	returns FALSE if bitmap saving is not supported by the plugin at all.
*/

static BOOL DLL_CALLCONV
SupportsExportDepth(int depth) {
	return FALSE;
}

static BOOL DLL_CALLCONV 
SupportsExportType(FREE_IMAGE_TYPE type) {
	return FALSE;
}

static BOOL DLL_CALLCONV
SupportsNoPixels() {
	return TRUE;
}

// ----------------------------------------------------------

/*!
    Loads a bitmap into memory. On entry it is assumed that
	the bitmap to be loaded is of the correct type. If the bitmap
	is of an incorrect type, the plugin might not gracefully fail but
	crash or enter an endless loop. It is also assumed that all
	the bitmap data is available at one time. If the bitmap is not complete,
	for example because it is being downloaded while loaded, the plugin
	might also not gracefully fail.

	The Load function has the following parameters:

    The first parameter (FreeImageIO *io) is a structure providing
	function pointers in order to make use of FreeImage's IO redirection. Using
	FreeImage's file i/o functions instead of standard ones it is garantueed
	that all bitmap types, both current and future ones, can be loaded from
	memory, file cabinets, the internet and more. The second parameter (fi_handle handle)
	is a companion of FreeImageIO and can be best compared with the standard FILE* type,
	in a generalized form.

	The third parameter (int page) indicates wether we will be loading a certain page
	in the bitmap or if we will load the default one. This parameter is only used if
	the plugin supports multi-paged bitmaps, e.g. cabinet bitmaps that contain a series
	of images or pages. If the plugin does support multi-paging, the page parameter
	can contain either a number higher or equal to 0 to load a certain page, or -1 to 
	load the default page. If the plugin does not support multi-paging,
	the page parameter is always -1.
	
	The fourth parameter (int flags) manipulates the load function to load a bitmap
	in a certain way. Every plugin has a different flag parameter with different meanings.

	The last parameter (void *data) can contain a special data block used when
	the file is read multi-paged. Because not every plugin supports multi-paging
	not every plugin will use the data parameter and it will be set to NULL.However,
	when the plugin does support multi-paging the parameter contains a pointer to a
	block of data allocated by the Open function.
*/

static FIBITMAP * DLL_CALLCONV
Load(FreeImageIO *io, fi_handle handle, int page, int flags, void *data) {
	FIBITMAP *dib = NULL;
	BYTE *bits;			  // Pointer to dib data
	RGBQUAD *pal;		  // Pointer to dib palette
	BYTE *line = NULL;	  // PCX raster line
	BYTE *ReadBuf = NULL; // buffer;
	BOOL bIsRLE;		  // True if the file is run-length encoded

	if(!handle) {
		return NULL;
	}

	BOOL header_only = (flags & FIF_LOAD_NOPIXELS) == FIF_LOAD_NOPIXELS;

	try {
		// check PCX identifier

		long start_pos = io->tell_proc(handle);
		BOOL validated = pcx_validate(io, handle);		
		io->seek_proc(handle, start_pos, SEEK_SET);
		if(!validated) {
			throw FI_MSG_ERROR_MAGIC_NUMBER;
		}

		// process the header

		PCXHEADER header;

		if(io->read_proc(&header, sizeof(PCXHEADER), 1, handle) != 1) {
			throw FI_MSG_ERROR_PARSING;
		}
#ifdef FREEIMAGE_BIGENDIAN
		SwapHeader(&header);
#endif

		// allocate a new DIB

		unsigned width = header.window[2] - header.window[0] + 1;
		unsigned height = header.window[3] - header.window[1] + 1;