PNGLoader.cpp
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	#include <echo/Resource/PNGLoader.h>
	#include <echo/FileSystem/File.h>
	#include <iostream>

	namespace Echo
	{
	png_voidp PngAlloc(png_structp p, png_size_t s)
	{
	png_voidp d = (png_voidp) (new u8[s]);
	return d;
	}

	void PngFree(png_structp p, png_voidp s)
	{
	u8* u8p = reinterpret_cast<u8*> (s);
	delete [] u8p;
	}

	void PngRead(png_structp png_ptr, png_bytep data, png_size_t length)
	{
	voidp read_io_ptr = png_get_io_ptr(png_ptr);
	if(read_io_ptr)
	{
	File& file = reinterpret_cast<File> (read_io_ptr);
	file.Read(data, 1, (u32) length);
	}
	}

	PNGLoader::PNGLoader() : mWidth(0), mHeight(0), mFormat(Texture::Formats::UNKNOWN), mFile(0)
	{}

	PNGLoader::~PNGLoader()
	{}

	bool PNGLoader::ProcessFile(File& textureFile)
	{
	mFile = 0;
	mCurrentRow = 0;

	if(!textureFile.IsOpen())
	{
	std::cout << "PNGLoader: Error input file is not open: " << textureFile.GetFileName() << std::endl;
	return false;
	}

	std::cout << "LoadPNG: " << textureFile.GetFileName() << std::endl;

	u8 header[8];

	//Read first 8 bytes - if we couldn't then that really sucks
	if(textureFile.Read((void*) (&header), 1, 8) < 8)
	{
	std::cout << "PNGLoader: Failed to read in first 8 bytes: " << textureFile.GetFileName() << std::endl;
	return 0;
	}

	//Check the file is a PNG
	bool is_png = !png_sig_cmp(header, 0, 8);
	if(!is_png)
	{
	std::cout << "PNGLoader: File is not a PNG file: " << textureFile.GetFileName() << std::endl;
	return 0;
	}

	//Allocate memory for the png stuct and the info struct
	mPNGPtr = png_create_read_struct_2(PNG_LIBPNG_VER_STRING, 0, 0, 0, 0, PngAlloc, PngFree);
	if(!mPNGPtr)
	{
	std::cout << "PNGLoader: png_create_read_struct: " << textureFile.GetFileName() << std::endl;
	return 0;
	}

	mInfoPtr = png_create_info_struct(mPNGPtr);
	if(!mInfoPtr)
	{
	png_destroy_read_struct(&mPNGPtr, (png_infopp) 0, (png_infopp) 0);
	std::cout << "PNGLoader: png_create_info_struct:1: " << textureFile.GetFileName() << std::endl;
	return 0;
	}

	mEndInfo = png_create_info_struct(mPNGPtr);
	if(!mEndInfo)
	{
	png_destroy_read_struct(&mPNGPtr, &mInfoPtr, (png_infopp) 0);
	std::cout << "PNGLoader: png_create_info_struct:2: " << textureFile.GetFileName() << std::endl;
	return 0;
	}

	mFile = &textureFile;

	png_set_read_fn(mPNGPtr, mFile, PngRead);
	png_set_sig_bytes(mPNGPtr, 8);
	png_read_png(mPNGPtr, mInfoPtr, PNG_TRANSFORM_IDENTITY, NULL);

	if(mInfoPtr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
	{
	png_set_swap_alpha(mPNGPtr);
	}

	//We only support 8 bit channels at the moment
	if(mInfoPtr->bit_depth == 16)
	{
	png_set_strip_16(mPNGPtr);
	}

	mRowPointers = png_get_rows(mPNGPtr, mInfoPtr);
	mWidth = png_get_image_width(mPNGPtr, mInfoPtr);
	mHeight = png_get_image_height(mPNGPtr, mInfoPtr);

	mBytesPerPixel = png_get_channels(mPNGPtr, mInfoPtr);
	switch(mBytesPerPixel)
	{
	case 4:
	if(mInfoPtr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
	{
	mFormat = Texture::Formats::R8G8B8A8;
	}else
	if(mInfoPtr->color_type == PNG_COLOR_TYPE_RGB)
	{
	mFormat = Texture::Formats::R8G8B8X8;
	}
	break;
	case 3:
	mFormat = Texture::Formats::R8G8B8;
	break;
	case 2:
	//PNG_COLOR_TYPE_GRAY_ALPHA
	return false;
	break;
	case 1:
	//PNG_COLOR_TYPE_GRAY
	//PNG_COLOR_TYPE_PALETTE
	return false;
	break;
	}
	return true;
	}

	std::string PNGLoader::GetFileExtension() const
	{
	return "png";
	}

	u32 PNGLoader::GetWidth() const
	{
	return mWidth;
	}

	u32 PNGLoader::GetHeight() const
	{
	return mHeight;
	}

	Texture::Format PNGLoader::GetFormat() const
	{
	return mFormat;
	}

	bool PNGLoader::GetLoadInverted() const
	{
	return false;
	}

	void PNGLoader::ReadLine(u8* lineStart, u32 maxLength)
	{
	if(!mFile)
	{
	return;
	}

	u32 widthBytes = std::min(mWidth * mBytesPerPixel, maxLength);
	//copy the data
	for(u32 c = 0; c < widthBytes; ++c)
	{
	lineStart[c] = mRowPointers[mCurrentRow][c];
	}
	mCurrentRow++;
	}

	void PNGLoader::CleanUp()
	{
	png_destroy_read_struct(&mPNGPtr, &mInfoPtr, (png_infopp) 0);
	}
	}

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