// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.

#include "ImageWrapperPrivatePCH.h"


#if WITH_UNREALPNG


/** Only allow one thread to use libpng at a time (it's not thread safe) */
FCriticalSection GPNGSection;


/* Local helper classes
 *****************************************************************************/

/**
 * Guard that safely releases PNG reader resources.
 */
class PNGReadGuard
{
public:
	PNGReadGuard( png_structp* InReadStruct, png_infop* InInfo )
		: png_ptr(InReadStruct)
		, info_ptr(InInfo)
		, PNGRowPointers(NULL)
	{
	}

	~PNGReadGuard()
	{
		if (PNGRowPointers != NULL)
		{
			png_free( *png_ptr, *PNGRowPointers );
		}
		png_destroy_read_struct( png_ptr, info_ptr, NULL );
	}

	void SetRowPointers( png_bytep** InRowPointers )
	{
		PNGRowPointers = InRowPointers;
	}

private:
	png_structp* png_ptr;
	png_infop* info_ptr;
	png_bytep** PNGRowPointers;
};


/**
 * Guard that safely releases PNG Writer resources
 */
class PNGWriteGuard
{
public:
	PNGWriteGuard( png_structp* InWriteStruct, png_infop* InInfo )
		: PNGWriteStruct(InWriteStruct)
		, info_ptr(InInfo)
		, PNGRowPointers(NULL)
	{
	}

	~PNGWriteGuard()
	{
		if (PNGRowPointers != NULL)
		{
			png_free( *PNGWriteStruct, *PNGRowPointers );
		}
		png_destroy_write_struct( PNGWriteStruct, info_ptr );
	}

	void SetRowPointers( png_bytep** InRowPointers )
	{
		PNGRowPointers = InRowPointers;
	}

private:
	png_structp* PNGWriteStruct;
	png_infop* info_ptr;
	png_bytep** PNGRowPointers;
};


/* FPngImageWrapper structors
 *****************************************************************************/

FPngImageWrapper::FPngImageWrapper()
	: FImageWrapperBase()
	, ReadOffset( 0 )
	, ColorType(0)
	, Channels(0)
{ }


/* FImageWrapper interface
 *****************************************************************************/

void FPngImageWrapper::Compress( int32 Quality )
{
	if (!CompressedData.Num())
	{
		// thread safety
		FScopeLock PNGLock(&GPNGSection);

		check(RawData.Num());
		check(Width > 0);
		check(Height > 0);

		// Reset to the beginning of file so we can use png_read_png(), which expects to start at the beginning.
		ReadOffset = 0;

		png_structp png_ptr	= png_create_write_struct( PNG_LIBPNG_VER_STRING, this, FPngImageWrapper::user_error_fn, FPngImageWrapper::user_warning_fn );
		check(png_ptr);

		png_infop info_ptr	= png_create_info_struct( png_ptr );
		check(info_ptr);

		PNGWriteGuard PNGGuard(&png_ptr, &info_ptr);
		{
			png_set_compression_level(png_ptr, Z_BEST_SPEED);
			png_set_IHDR(png_ptr, info_ptr, Width, Height, RawBitDepth, (RawFormat == ERGBFormat::Gray) ? PNG_COLOR_TYPE_GRAY : PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
			png_set_write_fn(png_ptr, this, FPngImageWrapper::user_write_compressed, FPngImageWrapper::user_flush_data);
			png_bytep* row_pointers = (png_bytep*) png_malloc( png_ptr, Height*sizeof(png_bytep) );

			const uint32 PixelChannels = (RawFormat == ERGBFormat::Gray) ? 1 : 4;
			const uint32 BytesPerPixel = (RawBitDepth * PixelChannels) / 8;
			const uint32 BytesPerRow = BytesPerPixel * Width;

			PNGGuard.SetRowPointers( &row_pointers );
			for (int32 i = 0; i < Height; i++)
			{
				row_pointers[i]= &RawData[i * BytesPerRow];
			}
			png_set_rows(png_ptr, info_ptr, row_pointers);

			uint32 Transform = (RawFormat == ERGBFormat::BGRA) ? PNG_TRANSFORM_BGR : PNG_TRANSFORM_IDENTITY;

			// PNG files store 16-bit pixels in network byte order (big-endian, ie. most significant bits first).
#if PLATFORM_LITTLE_ENDIAN
			// We're little endian so we need to swap
			if (RawBitDepth == 16)
			{
				Transform |= PNG_TRANSFORM_SWAP_ENDIAN;
			}
#endif

			png_write_png(png_ptr, info_ptr, Transform, NULL);
		}
	}
}


void FPngImageWrapper::Reset( )
{
	FImageWrapperBase::Reset();

	ReadOffset = 0;
	ColorType = 0;
	Channels = 0;
}


bool FPngImageWrapper::SetCompressed( const void* InCompressedData, int32 InCompressedSize )
{
	bool bResult = FImageWrapperBase::SetCompressed( InCompressedData, InCompressedSize );

	return bResult && LoadPNGHeader();	// Fetch the variables from the header info
}


void FPngImageWrapper::Uncompress( const ERGBFormat::Type InFormat, const int32 InBitDepth )
{
	if( !RawData.Num() || InFormat != RawFormat || InBitDepth != RawBitDepth)
	{
		check( CompressedData.Num() );
		UncompressPNGData( InFormat, InBitDepth );
	}
}

void FPngImageWrapper::UncompressPNGData( const ERGBFormat::Type InFormat, const int32 InBitDepth )
{
	// thread safety
	FScopeLock PNGLock(&GPNGSection);

	check( CompressedData.Num() );
	check( Width > 0 );
	check( Height > 0 );

	// Note that PNGs on PC tend to be BGR
	check( InFormat == ERGBFormat::BGRA || InFormat == ERGBFormat::RGBA || InFormat == ERGBFormat::Gray )	// Other formats unsupported at present
	check( InBitDepth == 8 || InBitDepth == 16 )	// Other formats unsupported at present

	// Reset to the beginning of file so we can use png_read_png(), which expects to start at the beginning.
	ReadOffset = 0;
		
	png_structp png_ptr	= png_create_read_struct_2( PNG_LIBPNG_VER_STRING, this, FPngImageWrapper::user_error_fn, FPngImageWrapper::user_warning_fn, NULL, FPngImageWrapper::user_malloc, FPngImageWrapper::user_free);
	check( png_ptr );

	png_infop info_ptr	= png_create_info_struct( png_ptr );
	check( info_ptr );
	PNGReadGuard PNGGuard( &png_ptr, &info_ptr );
	{
		if (ColorType == PNG_COLOR_TYPE_PALETTE)
		{
			png_set_palette_to_rgb(png_ptr);
		}

		if ((ColorType & PNG_COLOR_MASK_COLOR) == 0 && BitDepth < 8)
		{
			png_set_expand_gray_1_2_4_to_8(png_ptr);
		}

		// Insert alpha channel with full opacity for RGB images without alpha
		if ((ColorType & PNG_COLOR_MASK_ALPHA) == 0 && (InFormat == ERGBFormat::BGRA || InFormat == ERGBFormat::RGBA))
		{
			// png images don't set PNG_COLOR_MASK_ALPHA if they have alpha from a tRNS chunk, but png_set_add_alpha seems to be safe regardless
			if ((ColorType & PNG_COLOR_MASK_COLOR) == 0)
			{
				png_set_tRNS_to_alpha(png_ptr);
			}
			else if (ColorType == PNG_COLOR_TYPE_PALETTE)
			{
				png_set_tRNS_to_alpha(png_ptr);
			}
			if (InBitDepth == 8)
			{
				png_set_add_alpha(png_ptr, 0xff , PNG_FILLER_AFTER);
			}
			else if (InBitDepth == 16)
			{
				png_set_add_alpha(png_ptr, 0xffff , PNG_FILLER_AFTER);
			}
		}

		// Calculate Pixel Depth
		const uint32 PixelChannels = (InFormat == ERGBFormat::Gray) ? 1 : 4;
		const uint32 BytesPerPixel = (InBitDepth * PixelChannels) / 8;
		const uint32 BytesPerRow = BytesPerPixel * Width;
		RawData.Empty(Height * BytesPerRow);
		RawData.AddUninitialized(Height * BytesPerRow);

		png_set_read_fn( png_ptr, this, FPngImageWrapper::user_read_compressed );

		png_bytep* row_pointers = (png_bytep*) png_malloc( png_ptr, Height*sizeof(png_bytep) );
		PNGGuard.SetRowPointers(&row_pointers);
		for (int32 i = 0; i < Height; i++)
		{
			row_pointers[i]= &RawData[i * BytesPerRow];
		}
		png_set_rows(png_ptr, info_ptr, row_pointers);

		uint32 Transform = (InFormat == ERGBFormat::BGRA) ? PNG_TRANSFORM_BGR : PNG_TRANSFORM_IDENTITY;
			
		// PNG files store 16-bit pixels in network byte order (big-endian, ie. most significant bits first).
#if PLATFORM_LITTLE_ENDIAN
		// We're little endian so we need to swap
		if (BitDepth == 16)
		{
			Transform |= PNG_TRANSFORM_SWAP_ENDIAN;
		}
#endif

		// Convert grayscale png to RGB if requested
		if ((ColorType & PNG_COLOR_MASK_COLOR) == 0 &&
			(InFormat == ERGBFormat::RGBA || InFormat == ERGBFormat::BGRA))
		{
			Transform |= PNG_TRANSFORM_GRAY_TO_RGB;
		}

		// Convert RGB png to grayscale if requested
		if ((ColorType & PNG_COLOR_MASK_COLOR) != 0 && InFormat == ERGBFormat::Gray)
		{
			png_set_rgb_to_gray_fixed(png_ptr, 2 /* warn if image is in color */, -1, -1);
		}

		// Strip alpha channel if requested output is grayscale
		if (InFormat == ERGBFormat::Gray)
		{
			// this is not necessarily the best option, instead perhaps:
			// png_color background = {0,0,0};
			// png_set_background(png_ptr, &background, PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
			Transform |= PNG_TRANSFORM_STRIP_ALPHA;
		}

		// Reduce 16-bit to 8-bit if requested
		if (BitDepth == 16 && InBitDepth == 8)
		{
#if PNG_LIBPNG_VER >= 10504
			check(0); // Needs testing
			Transform |= PNG_TRANSFORM_SCALE_16;
#else
			Transform |= PNG_TRANSFORM_STRIP_16;
#endif
		}

		// Increase 8-bit to 16-bit if requested
		if (BitDepth <= 8 && InBitDepth == 16)
		{
#if PNG_LIBPNG_VER >= 10504
			check(0); // Needs testing
			Transform |= PNG_TRANSFORM_EXPAND_16
#else
			// Expanding 8-bit images to 16-bit via transform needs a libpng update
			check(0);
#endif
		}

		png_read_png(png_ptr, info_ptr, Transform, NULL);
	}

	RawFormat = InFormat;
	RawBitDepth = InBitDepth;
}

/* FPngImageWrapper implementation
 *****************************************************************************/


bool FPngImageWrapper::IsPNG() const
{
	check( CompressedData.Num() );

	const int32 PNGSigSize = sizeof(png_size_t);

	if (CompressedData.Num() > PNGSigSize)
	{
		png_size_t PNGSignature = *reinterpret_cast<const png_size_t*>(CompressedData.GetData());
		return (0 == png_sig_cmp(reinterpret_cast<png_bytep>(&PNGSignature), 0, PNGSigSize));
	}

	return false;
}


bool FPngImageWrapper::LoadPNGHeader()
{
	check(CompressedData.Num());

	// Test whether the data this PNGLoader is pointing at is a PNG or not.
	if (IsPNG())
	{
		// thread safety
		FScopeLock PNGLock(&GPNGSection);

		png_structp png_ptr = png_create_read_struct_2( PNG_LIBPNG_VER_STRING, this, FPngImageWrapper::user_error_fn, FPngImageWrapper::user_warning_fn, NULL, FPngImageWrapper::user_malloc, FPngImageWrapper::user_free );
		check(png_ptr);

		png_infop info_ptr = png_create_info_struct( png_ptr );
		check(info_ptr);

		PNGReadGuard PNGGuard(&png_ptr, &info_ptr);
		{
			png_set_read_fn(png_ptr, this, FPngImageWrapper::user_read_compressed);

			png_read_info(png_ptr, info_ptr);

			Width = info_ptr->width;
			Height = info_ptr->height;
			ColorType = info_ptr->color_type;
			BitDepth = info_ptr->bit_depth;
			Channels = info_ptr->channels;
			Format = (ColorType & PNG_COLOR_MASK_COLOR) ? ERGBFormat::RGBA : ERGBFormat::Gray;
		}

		return true;
	}

	return false;
}


/* FPngImageWrapper static implementation
 *****************************************************************************/

void FPngImageWrapper::user_read_compressed( png_structp png_ptr, png_bytep data, png_size_t length )
{
	FPngImageWrapper* ctx = (FPngImageWrapper*) png_get_io_ptr(png_ptr);
	check(ctx->ReadOffset + length <= (uint32)ctx->CompressedData.Num());

	FMemory::Memcpy(data, &ctx->CompressedData[ctx->ReadOffset], length);

	ctx->ReadOffset += length;
}


void FPngImageWrapper::user_write_compressed( png_structp png_ptr, png_bytep data, png_size_t length )
{
	FPngImageWrapper* ctx = (FPngImageWrapper*) png_get_io_ptr(png_ptr);

	int32 Offset = ctx->CompressedData.AddUninitialized( length);
	FMemory::Memcpy(&ctx->CompressedData[Offset], data, length);
}


void FPngImageWrapper::user_flush_data( png_structp png_ptr )
{
}


void FPngImageWrapper::user_error_fn( png_structp png_ptr, png_const_charp error_msg )
{
	FPngImageWrapper* ctx = (FPngImageWrapper*)png_get_io_ptr( png_ptr );
	FString ErrorMsg = ANSI_TO_TCHAR(error_msg);
	ctx->SetError(*ErrorMsg);

	UE_LOG(LogImageWrapper, Error, TEXT("PNG Error: %s"), *ErrorMsg);
}


void FPngImageWrapper::user_warning_fn( png_structp png_ptr, png_const_charp warning_msg )
{
	UE_LOG(LogImageWrapper, Warning, TEXT("PNG Warning: %s"), ANSI_TO_TCHAR(warning_msg));
}

void* FPngImageWrapper::user_malloc( png_structp /*png_ptr*/, png_size_t size)
{
	check(size > 0);
	return FMemory::Malloc(size);
}

void FPngImageWrapper::user_free(png_structp /*png_ptr*/, png_voidp struct_ptr )
{
	check(struct_ptr);
	FMemory::Free(struct_ptr);
}


#endif	//WITH_UNREALPNG