vbagx/source/utils/pngu.c

/****************************************************************************
 *
 * PNGU
 * 
 * Original author: frontier (http://frontier-dev.net)
 * This is Tantric's modified/condensed version + RGB565 decoder from original
 *
 ***************************************************************************/

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#include "pngu.h"
#include <png.h>

// Constants
#define PNGU_SOURCE_BUFFER				1
#define PNGU_SOURCE_DEVICE				2

// Color types
#define PNGU_COLOR_TYPE_GRAY			1
#define PNGU_COLOR_TYPE_GRAY_ALPHA		2
#define PNGU_COLOR_TYPE_PALETTE			3
#define PNGU_COLOR_TYPE_RGB				4
#define PNGU_COLOR_TYPE_RGB_ALPHA		5
#define PNGU_COLOR_TYPE_UNKNOWN 		6

// PNGU Image context struct
struct _IMGCTX
{
	int source;
	void *buffer;
	char *filename;
	u32 cursor;

	u32 propRead;
	PNGUPROP prop;

	u32 infoRead;
	png_structp png_ptr;
	png_infop info_ptr;
	FILE *fd;
	
	png_bytep *row_pointers;
	png_bytep img_data;
};

// PNGU Implementation

static void pngu_free_info (IMGCTX ctx)
{
	if (ctx->infoRead)
	{
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);

		png_destroy_read_struct (&(ctx->png_ptr), &(ctx->info_ptr), (png_infopp)NULL);

		ctx->infoRead = 0;
	}
}

// Custom data provider function used for reading from memory buffers.
static void pngu_read_data_from_buffer (png_structp png_ptr, png_bytep data, png_size_t length)
{
	IMGCTX ctx = (IMGCTX) png_get_io_ptr (png_ptr);
	memcpy (data, ctx->buffer + ctx->cursor, length);
	ctx->cursor += length;
}

// Custom data writer function used for writing to memory buffers.
static void pngu_write_data_to_buffer (png_structp png_ptr, png_bytep data, png_size_t length)
{
	IMGCTX ctx = (IMGCTX) png_get_io_ptr (png_ptr);
	memcpy (ctx->buffer + ctx->cursor, data, length);
	ctx->cursor += length;
}

// Custom data flusher function used for writing to memory buffers.
static void pngu_flush_data_to_buffer (png_structp png_ptr)
{
	// Nothing to do here
}

static int pngu_info (IMGCTX ctx)
{
	png_byte magic[8];
	png_uint_32 width;
	png_uint_32 height;
	png_color_16p background;
	png_bytep trans;
	png_color_16p trans_values;
	int scale, i;

	// Check if there is a file selected and if it is a valid .png
	if (ctx->source == PNGU_SOURCE_BUFFER)
		memcpy (magic, ctx->buffer, 8);

	else if (ctx->source == PNGU_SOURCE_DEVICE)
	{
		// Load first 8 bytes into magic buffer
        if (fread (magic, 1, 8, ctx->fd) != 8)
		{
			fclose (ctx->fd);
			return PNGU_CANT_READ_FILE;
		}
	}

	else
		return PNGU_NO_FILE_SELECTED;;

	if (png_sig_cmp(magic, 0, 8) != 0)
	{
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
		return PNGU_FILE_IS_NOT_PNG;
	}

	// Allocation of libpng structs
	ctx->png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!(ctx->png_ptr))
	{
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
        return PNGU_LIB_ERROR;
	}

    ctx->info_ptr = png_create_info_struct (ctx->png_ptr);
    if (!(ctx->info_ptr))
    {
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
        png_destroy_read_struct (&(ctx->png_ptr), (png_infopp)NULL, (png_infopp)NULL);
        return PNGU_LIB_ERROR;
    }

	if (ctx->source == PNGU_SOURCE_BUFFER)
	{
		// Installation of our custom data provider function
		ctx->cursor = 0;
		png_set_read_fn (ctx->png_ptr, ctx, pngu_read_data_from_buffer);
	}
	else if (ctx->source == PNGU_SOURCE_DEVICE)
	{
		// Default data provider uses function fread, so it needs to use our FILE*
		png_init_io (ctx->png_ptr, ctx->fd);
		png_set_sig_bytes (ctx->png_ptr, 8); // We have read 8 bytes already to check PNG authenticity
	}

	// Read png header
	png_read_info (ctx->png_ptr, ctx->info_ptr);

	// Query image properties if they have not been queried before
	if (!ctx->propRead)
	{
		int ctxNumTrans;

		png_get_IHDR(ctx->png_ptr, ctx->info_ptr, &width, &height,
					(int *) &(ctx->prop.imgBitDepth), 
					(int *) &(ctx->prop.imgColorType),
					NULL, NULL, NULL);

		ctx->prop.imgWidth = width;
		ctx->prop.imgHeight = height;
		switch (ctx->prop.imgColorType)
		{
			case PNG_COLOR_TYPE_GRAY:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_GRAY;
				break;
			case PNG_COLOR_TYPE_GRAY_ALPHA:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_GRAY_ALPHA;
				break;
			case PNG_COLOR_TYPE_PALETTE:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_PALETTE;
				break;
			case PNG_COLOR_TYPE_RGB:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_RGB;
				break;
			case PNG_COLOR_TYPE_RGB_ALPHA:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_RGB_ALPHA;
				break;
			default:
				ctx->prop.imgColorType = PNGU_COLOR_TYPE_UNKNOWN;
				break;
		}

		// Constant used to scale 16 bit values to 8 bit values
		scale = 0;
		if (ctx->prop.imgBitDepth == 16)
			scale = 8;

		// Query background color, if any.
		ctx->prop.validBckgrnd = 0;

		switch(ctx->prop.imgColorType)
		{
			case PNGU_COLOR_TYPE_RGB:
			case PNGU_COLOR_TYPE_RGB_ALPHA:
			{
				if(png_get_bKGD (ctx->png_ptr, ctx->info_ptr, &background)){
					ctx->prop.validBckgrnd = 1;
					ctx->prop.bckgrnd.r = background->red >> scale;
					ctx->prop.bckgrnd.g = background->green >> scale;
					ctx->prop.bckgrnd.b = background->blue >> scale;
				}
				
				// Query list of transparent colors, if any.
				ctx->prop.numTrans = 0;
				ctx->prop.trans = NULL;
				
				if(png_get_tRNS (ctx->png_ptr, ctx->info_ptr, &trans, (int *) &(ctx->prop.numTrans), &trans_values)){
					ctxNumTrans = ctx->prop.numTrans;
					if(ctxNumTrans){
						ctx->prop.trans = malloc (sizeof (PNGUCOLOR) * ctxNumTrans);
						if (ctx->prop.trans)
							for (i = 0; i < ctxNumTrans; i++)
							{
								ctx->prop.trans[i].r = trans_values[i].red >> scale;
								ctx->prop.trans[i].g = trans_values[i].green >> scale;
								ctx->prop.trans[i].b = trans_values[i].blue >> scale;
							}
						else
							ctx->prop.numTrans = 0;
					}
				}
				
			}
			break;
			
			case PNGU_COLOR_TYPE_GRAY:
			case PNGU_COLOR_TYPE_GRAY_ALPHA:
			{
				if(png_get_bKGD (ctx->png_ptr, ctx->info_ptr, &background)){
					ctx->prop.validBckgrnd = 1;
					ctx->prop.bckgrnd.r = 
					ctx->prop.bckgrnd.g = 
					ctx->prop.bckgrnd.b = background->gray >> scale;
				}
				
				// Query list of transparent colors, if any.
				ctx->prop.numTrans = 0;
				ctx->prop.trans = NULL;
				
				if(png_get_tRNS (ctx->png_ptr, ctx->info_ptr, &trans, (int *) &(ctx->prop.numTrans), &trans_values)){
					ctxNumTrans = ctx->prop.numTrans;
					if(ctxNumTrans){
						ctx->prop.trans = malloc (sizeof (PNGUCOLOR) * ctxNumTrans);
						if (ctx->prop.trans)
							for (i = 0; i < ctxNumTrans; i++)
								ctx->prop.trans[i].r = 
								ctx->prop.trans[i].g = 
								ctx->prop.trans[i].b = trans_values[i].gray >> scale;
						else
							ctx->prop.numTrans = 0;
					}
				}
				
			}
			break;
			
			default:
			
			// It was none of those things, 
			{
				// Query list of transparent colors, if any.
				ctx->prop.numTrans = 0;
				ctx->prop.trans = NULL;
			}
			break;
		}

		ctx->propRead = 1;
	}

	// Success
	ctx->infoRead = 1;

	return PNGU_OK;
}

static int pngu_decode (IMGCTX ctx, u32 width, u32 height, u32 stripAlpha)
{
	png_uint_32 rowbytes;
	png_uint_32 i, propImgHeight;

	// Read info if it hasn't been read before
	if (!ctx->infoRead)
	{
		int c = pngu_info (ctx);
		if (c != PNGU_OK)
			return c;
	}

	// Check if the user has specified the real width and height of the image
	if ( (ctx->prop.imgWidth != width) || (ctx->prop.imgHeight != height) )
		return PNGU_INVALID_WIDTH_OR_HEIGHT;

	// Check if color type is supported by PNGU
	if (ctx->prop.imgColorType == PNGU_COLOR_TYPE_UNKNOWN)
		return PNGU_UNSUPPORTED_COLOR_TYPE;

	// Scale 16 bit samples to 8 bit
	if (ctx->prop.imgBitDepth == 16)
        png_set_strip_16 (ctx->png_ptr);

	// Remove alpha channel if we don't need it
	if (stripAlpha && ((ctx->prop.imgColorType == PNGU_COLOR_TYPE_RGB_ALPHA) || (ctx->prop.imgColorType == PNGU_COLOR_TYPE_GRAY_ALPHA)))
        png_set_strip_alpha (ctx->png_ptr);

	// Expand 1, 2 and 4 bit samples to 8 bit
	if (ctx->prop.imgBitDepth < 8)
        png_set_packing (ctx->png_ptr);

	// Transform grayscale images to RGB
	if ( (ctx->prop.imgColorType == PNGU_COLOR_TYPE_GRAY) || (ctx->prop.imgColorType == PNGU_COLOR_TYPE_GRAY_ALPHA) )
		png_set_gray_to_rgb (ctx->png_ptr);
		
	// Transform palette images to RGB
	if (ctx->prop.imgColorType == PNGU_COLOR_TYPE_PALETTE)
		png_set_palette_to_rgb(ctx->png_ptr);

	// Flush transformations
	png_read_update_info (ctx->png_ptr, ctx->info_ptr);

	// Allocate memory to store the image
	rowbytes = png_get_rowbytes (ctx->png_ptr, ctx->info_ptr);

	if (rowbytes & 3)
		rowbytes = ((rowbytes >> 2) + 1) << 2; // Add extra padding so each row starts in a 4 byte boundary

	ctx->img_data = malloc (rowbytes * ctx->prop.imgHeight);
	if (!ctx->img_data)
	{
		pngu_free_info (ctx);
		return PNGU_LIB_ERROR;
	}

	ctx->row_pointers = malloc (sizeof (png_bytep) * ctx->prop.imgHeight);
	if (!ctx->row_pointers)
	{
		free (ctx->img_data);
		pngu_free_info (ctx);
		return PNGU_LIB_ERROR;
	}

	propImgHeight = ctx->prop.imgHeight;
	for (i = 0; i < propImgHeight; ++i)
		ctx->row_pointers[i] = ctx->img_data + (i * rowbytes);

	// Transform the image and copy it to our allocated memory
	png_read_image (ctx->png_ptr, ctx->row_pointers);

	// Free resources
	pngu_free_info (ctx);

	// Success
	return PNGU_OK;
}

static inline u32 coordsRGBA8(u32 x, u32 y, u32 w)
{
	return ((((y >> 2) * (w >> 2) + (x >> 2)) << 5) + ((y & 3) << 2) + (x & 3)) << 1;
}

static u8 * PNGU_DecodeTo4x4RGBA8 (IMGCTX ctx, u32 width, u32 height, int * dstWidth, int * dstHeight, u8 *dstPtr, int maxWidth, int maxHeight)
{
	u8 default_alpha = 255;
	u8 *dst;
	int x, y, x2, y2, offset;
	int xRatio = 0, yRatio = 0;
	png_byte *pixel;

	if (pngu_decode (ctx, width, height, 0) != PNGU_OK)
		return NULL;

	int newWidth = width;
	int newHeight = height;

	if((maxWidth > 0 && width > maxWidth) || (maxHeight > 0 && height > maxHeight))
	{
		float ratio = (float)width/(float)height;

		newWidth = maxWidth;
		newHeight = maxWidth/ratio;

		if(newHeight > maxHeight)
		{
			newWidth = maxHeight*ratio;
			newHeight = maxHeight;
		}
		xRatio = (int)((width<<16)/newWidth)+1;
		yRatio = (int)((height<<16)/newHeight)+1;
	}

	int padWidth = newWidth;
	int padHeight = newHeight;
	if(padWidth%4) padWidth += (4-padWidth%4);
	if(padHeight%4) padHeight += (4-padHeight%4);

	int len = (padWidth * padHeight) << 2;
	if(len%32) len += (32-len%32);

	if(dstPtr)
		dst = dstPtr; // use existing allocation
	else
		dst = memalign (32, len);

	if(!dst)
		return NULL;

	for (y = 0; y < padHeight; y++)
	{
		for (x = 0; x < padWidth; x++)
		{
			offset = coordsRGBA8(x, y, padWidth);

			if(y >= newHeight || x >= newWidth)
			{
				dst[offset] = 0;
				dst[offset+1] = 255;
				dst[offset+32] = 255;
				dst[offset+33] = 255;
			}
			else
			{
				if(xRatio > 0)
				{
					x2 = ((x*xRatio)>>16);
					y2 = ((y*yRatio)>>16);
				}

				if (ctx->prop.imgColorType == PNGU_COLOR_TYPE_GRAY_ALPHA || 
					ctx->prop.imgColorType == PNGU_COLOR_TYPE_RGB_ALPHA)
				{
					if(xRatio > 0)
						pixel = &(ctx->row_pointers[y2][x2*4]);
					else
						pixel = &(ctx->row_pointers[y][x*4]);

					dst[offset] = pixel[3]; // Alpha
					dst[offset+1] = pixel[0]; // Red
					dst[offset+32] = pixel[1]; // Green
					dst[offset+33] = pixel[2]; // Blue
				}
				else
				{
					if(xRatio > 0)
						pixel = &(ctx->row_pointers[y2][x2*3]);
					else
						pixel = &(ctx->row_pointers[y][x*3]);

					dst[offset] = default_alpha; // Alpha
					dst[offset+1] = pixel[0]; // Red
					dst[offset+32] = pixel[1]; // Green
					dst[offset+33] = pixel[2]; // Blue
				}
			}
		}
	}

	// Free resources
	free (ctx->img_data);
	free (ctx->row_pointers);

	*dstWidth = padWidth;
	*dstHeight = padHeight;
	DCFlushRange(dst, len);
	return dst;
}

int PNGU_DecodeTo4x4RGB565 (IMGCTX ctx, u32 width, u32 height, void *buffer)
{
	int result;
	u32 x, y, qwidth, qheight;

	// width and height need to be divisible by four
	if ((width % 4) || (height % 4))
		return PNGU_INVALID_WIDTH_OR_HEIGHT;

	result = pngu_decode (ctx, width, height, 1);
	if (result != PNGU_OK)
		return result;

	// Copy image to the output buffer
	qwidth = width / 4;
	qheight = height / 4;

	for (y = 0; y < qheight; y++)
		for (x = 0; x < qwidth; x++)
		{
			int blockbase = (y * qwidth + x) * 4;

			u64 field64 = *((u64 *)(ctx->row_pointers[y*4]+x*12));
			u64 field32 = (u64) *((u32 *)(ctx->row_pointers[y*4]+x*12+8));
			((u64 *) buffer)[blockbase] = 
				(((field64 & 0xF800000000000000ULL) | ((field64 & 0xFC000000000000ULL) << 3) | ((field64 & 0xF80000000000ULL) << 5)) | 
				(((field64 & 0xF800000000ULL) << 8) | ((field64 & 0xFC000000ULL) << 11) | ((field64 & 0xF80000ULL) << 13)) | 
				(((field64 & 0xF800ULL) << 16) | ((field64 & 0xFCULL) << 19) | ((field32 & 0xF8000000ULL) >> 11)) |
				(((field32 & 0xF80000ULL) >> 8) | ((field32 & 0xFC00ULL) >> 5) | ((field32 & 0xF8ULL) >> 3)));

			field64 = *((u64 *)(ctx->row_pointers[y*4+1]+x*12));
			field32 = (u64) *((u32 *)(ctx->row_pointers[y*4+1]+x*12+8));
			((u64 *) buffer)[blockbase+1] = 
				(((field64 & 0xF800000000000000ULL) | ((field64 & 0xFC000000000000ULL) << 3) | ((field64 & 0xF80000000000ULL) << 5)) | 
				(((field64 & 0xF800000000ULL) << 8) | ((field64 & 0xFC000000ULL) << 11) | ((field64 & 0xF80000ULL) << 13)) | 
				(((field64 & 0xF800ULL) << 16) | ((field64 & 0xFCULL) << 19) | ((field32 & 0xF8000000ULL) >> 11)) |
				(((field32 & 0xF80000ULL) >> 8) | ((field32 & 0xFC00ULL) >> 5) | ((field32 & 0xF8ULL) >> 3)));

			field64 = *((u64 *)(ctx->row_pointers[y*4+2]+x*12));
			field32 = (u64) *((u32 *)(ctx->row_pointers[y*4+2]+x*12+8));
			((u64 *) buffer)[blockbase+2] = 
				(((field64 & 0xF800000000000000ULL) | ((field64 & 0xFC000000000000ULL) << 3) | ((field64 & 0xF80000000000ULL) << 5)) | 
				(((field64 & 0xF800000000ULL) << 8) | ((field64 & 0xFC000000ULL) << 11) | ((field64 & 0xF80000ULL) << 13)) | 
				(((field64 & 0xF800ULL) << 16) | ((field64 & 0xFCULL) << 19) | ((field32 & 0xF8000000ULL) >> 11)) |
				(((field32 & 0xF80000ULL) >> 8) | ((field32 & 0xFC00ULL) >> 5) | ((field32 & 0xF8ULL) >> 3)));

			field64 = *((u64 *)(ctx->row_pointers[y*4+3]+x*12));
			field32 = (u64) *((u32 *)(ctx->row_pointers[y*4+3]+x*12+8));
			((u64 *) buffer)[blockbase+3] = 
				(((field64 & 0xF800000000000000ULL) | ((field64 & 0xFC000000000000ULL) << 3) | ((field64 & 0xF80000000000ULL) << 5)) | 
				(((field64 & 0xF800000000ULL) << 8) | ((field64 & 0xFC000000ULL) << 11) | ((field64 & 0xF80000ULL) << 13)) | 
				(((field64 & 0xF800ULL) << 16) | ((field64 & 0xFCULL) << 19) | ((field32 & 0xF8000000ULL) >> 11)) |
				(((field32 & 0xF80000ULL) >> 8) | ((field32 & 0xFC00ULL) >> 5) | ((field32 & 0xF8ULL) >> 3)));
		}
	
	// Free resources
	free (ctx->img_data);
	free (ctx->row_pointers);

	// Success
	return PNGU_OK;
}

IMGCTX PNGU_SelectImageFromBuffer (const void *buffer)
{
	IMGCTX ctx = NULL;

	if (!buffer)
		return NULL;

	ctx = malloc (sizeof (struct _IMGCTX));
	if (!ctx)
		return NULL;

	ctx->buffer = (void *) buffer;
	ctx->source = PNGU_SOURCE_BUFFER;
	ctx->cursor = 0;
	ctx->filename = NULL;
	ctx->propRead = 0;
	ctx->infoRead = 0;

	return ctx;
}

IMGCTX PNGU_SelectImageFromDevice (const char *filename)
{
	IMGCTX ctx = NULL;

	if (!filename)
		return NULL;

	ctx = malloc (sizeof (struct _IMGCTX));
	if (!ctx)
		return NULL;

	ctx->buffer = NULL;
	ctx->source = PNGU_SOURCE_DEVICE;
	ctx->cursor = 0;

	ctx->filename = malloc (strlen (filename) + 1);
	if (!ctx->filename)
	{
		free (ctx);
		return NULL;
	}
	strcpy(ctx->filename, filename);

	ctx->propRead = 0;
	ctx->infoRead = 0;

	return ctx;
}

void PNGU_ReleaseImageContext (IMGCTX ctx)
{
	if (!ctx)
		return;

	if (ctx->filename)
		free (ctx->filename);

	if ((ctx->propRead) && (ctx->prop.trans))
		free (ctx->prop.trans);

	pngu_free_info (ctx);
	free (ctx);
}

int PNGU_GetImageProperties (IMGCTX ctx, PNGUPROP *imgprop)
{
	int res;

	if (!ctx->propRead)
	{
		res = pngu_info (ctx);
		if (res != PNGU_OK)
			return res;
	}

	*imgprop = ctx->prop;
	return PNGU_OK;
}

u8 * DecodePNG(const u8 *src, int * width, int * height, u8 *dstPtr, int maxwidth, int maxheight)
{
	PNGUPROP imgProp;
	IMGCTX ctx = PNGU_SelectImageFromBuffer(src);
	u8 *dst = NULL;

	if(!ctx)
		return NULL;

	if(PNGU_GetImageProperties(ctx, &imgProp) == PNGU_OK)
		dst = PNGU_DecodeTo4x4RGBA8 (ctx, imgProp.imgWidth, imgProp.imgHeight, width, height, dstPtr, maxwidth, maxheight);

	PNGU_ReleaseImageContext (ctx);
	return dst;
}

u8 * DecodePNGFromFile(const char *filepath, int * width, int * height, u8 *dstPtr, int maxwidth, int maxheight)
{
	FILE *file = fopen (filepath, "rb");

	if (!file)
		return NULL;

	IMGCTX ctx = PNGU_SelectImageFromDevice(filepath);

	if(!ctx)
		return NULL;

	ctx->fd = file;
	PNGUPROP imgProp;
	u8 *dst = NULL;

	if(PNGU_GetImageProperties(ctx, &imgProp) == PNGU_OK && imgProp.imgWidth <= maxwidth && imgProp.imgHeight <= maxheight)
		dst = PNGU_DecodeTo4x4RGBA8 (ctx, imgProp.imgWidth, imgProp.imgHeight, width, height, dstPtr, maxwidth, maxheight);

	PNGU_ReleaseImageContext (ctx);
	return dst;
}

int PNGU_EncodeFromRGB (IMGCTX ctx, u32 width, u32 height, void *buffer, u32 stride)
{
	png_uint_32 rowbytes;
	u32 y;

	// Erase from the context any readed info
	pngu_free_info (ctx);
	ctx->propRead = 0;

	// Check if the user has selected a file to write the image
	if (ctx->source == PNGU_SOURCE_BUFFER);	

	else if (ctx->source == PNGU_SOURCE_DEVICE)
	{
		// Open file
		if (!(ctx->fd = fopen (ctx->filename, "wb")))
			return PNGU_CANT_OPEN_FILE;
	}

	else
		return PNGU_NO_FILE_SELECTED;

	// Allocation of libpng structs
	ctx->png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!(ctx->png_ptr))
	{
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
        return PNGU_LIB_ERROR;
	}

    ctx->info_ptr = png_create_info_struct (ctx->png_ptr);
    if (!(ctx->info_ptr))
    {
		png_destroy_write_struct (&(ctx->png_ptr), (png_infopp)NULL);
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
        return PNGU_LIB_ERROR;
    }

	if (ctx->source == PNGU_SOURCE_BUFFER)
	{
		// Installation of our custom data writer function
		ctx->cursor = 0;
		png_set_write_fn (ctx->png_ptr, ctx, pngu_write_data_to_buffer, pngu_flush_data_to_buffer);
	}
	else if (ctx->source == PNGU_SOURCE_DEVICE)
	{
		// Default data writer uses function fwrite, so it needs to use our FILE*
		png_init_io (ctx->png_ptr, ctx->fd);
	}

	// Setup output file properties
    png_set_IHDR (ctx->png_ptr, ctx->info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB, 
				PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

	// Allocate memory to store the image in RGB format
	rowbytes = width * 3;
	if (rowbytes % 4)
		rowbytes = ((rowbytes >>2) + 1) <<2; // Add extra padding so each row starts in a 4 byte boundary

	ctx->img_data = malloc(rowbytes * height);

	if (!ctx->img_data)
	{
		png_destroy_write_struct (&(ctx->png_ptr), (png_infopp)NULL);
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
		return PNGU_LIB_ERROR;
	}

	memset(ctx->img_data, 0, rowbytes * height);
	ctx->row_pointers = malloc (sizeof (png_bytep) * height);

	if (!ctx->row_pointers)
	{
		png_destroy_write_struct (&(ctx->png_ptr), (png_infopp)NULL);
		if (ctx->source == PNGU_SOURCE_DEVICE)
			fclose (ctx->fd);
		return PNGU_LIB_ERROR;
	}

	memset(ctx->row_pointers, 0, sizeof (png_bytep) * height);

	for (y = 0; y < height; ++y)
	{
		ctx->row_pointers[y] = buffer + (y * rowbytes);
	}

	// Tell libpng where is our image data
	png_set_rows (ctx->png_ptr, ctx->info_ptr, ctx->row_pointers);

	// Write file header and image data
	png_write_png (ctx->png_ptr, ctx->info_ptr, PNG_TRANSFORM_IDENTITY, NULL);

	// Tell libpng we have no more data to write
	png_write_end (ctx->png_ptr, (png_infop) NULL);

	// Free resources
	free (ctx->img_data);
	free (ctx->row_pointers);
	png_destroy_write_struct (&(ctx->png_ptr), &(ctx->info_ptr));
	if (ctx->source == PNGU_SOURCE_DEVICE)
		fclose (ctx->fd);

	// Success
	return ctx->cursor;
}

int PNGU_EncodeFromGXTexture (IMGCTX ctx, u32 width, u32 height, void *buffer, u32 stride)
{
	int res;
	u32 x, y, tmpy1, tmpy2, tmpyWid, tmpxy;

	unsigned char * ptr = (unsigned char*)buffer;
	unsigned char * tmpbuffer = malloc(width*height*3);

	if(!tmpbuffer)
		return PNGU_LIB_ERROR;

	memset(tmpbuffer, 0, width*height*3);
	png_uint_32 offset;
	
	for(y=0; y < height; y++)
	{
		tmpy1 = y * 640*3;
		tmpy2 = y%4 << 2;
		tmpyWid = (((y >> 2)<<4)*width);

		for(x=0; x < width; x++)
		{
			offset = tmpyWid + ((x >> 2)<<6) + ((tmpy2+ x%4 ) << 1);
			tmpxy = x * 3 + tmpy1;

			tmpbuffer[tmpxy  ] = ptr[offset+1]; // R
			tmpbuffer[tmpxy+1] = ptr[offset+32]; // G
			tmpbuffer[tmpxy+2] = ptr[offset+33]; // B
		}
	}
	
	res = PNGU_EncodeFromRGB (ctx, width, height, tmpbuffer, stride);
	free(tmpbuffer);
	return res;
}

int PNGU_EncodeFromEFB (IMGCTX ctx, u32 width, u32 height)
{
	int res;
	u32 x, y, tmpy1, tmpxy;
	GXColor color;

	unsigned char * tmpbuffer = malloc(width*height*3);

	if(!tmpbuffer)
		return PNGU_LIB_ERROR;

	for(y=0; y < height; y++)
	{
		tmpy1 = y * width * 3;

		for(x=0; x < width; x++)
		{
			tmpxy = x * 3 + tmpy1;
			GX_PeekARGB(x, y, &color);
			tmpbuffer[tmpxy  ] = color.r; // R
			tmpbuffer[tmpxy+1] = color.g; // G
			tmpbuffer[tmpxy+2] = color.b; // B
		}
	}

	res = PNGU_EncodeFromRGB (ctx, width, height, tmpbuffer, 0);
	free(tmpbuffer);
	return res;
}

// Added by libertyernie
int PNGU_EncodeFromLinearRGB565 (IMGCTX ctx, u32 width, u32 height, const void* buffer, int rowlength)
{
	int res;
	u32 x, y, tmpy1, tmpxy;

	u16 * src = (u16 *)buffer;
	unsigned char * tmpbuffer = malloc(width*height*3);

	if(!tmpbuffer)
		return PNGU_LIB_ERROR;

	for(y=0; y < height; y++)
	{
		tmpy1 = y * width * 3;

		for(x=0; x < width; x++)
		{
			tmpxy = x * 3 + tmpy1;
			u16 color = *src++;
			tmpbuffer[tmpxy  ] = (color >> 11) << 3; // R
			tmpbuffer[tmpxy+1] = ((color >> 6) & 31) << 3; // G - discard least significant byte
			tmpbuffer[tmpxy+2] = (color & 31) << 3; // B
		}
		
		if (rowlength > width) {
			src += (rowlength - width);
		}
	}

	res = PNGU_EncodeFromRGB (ctx, width, height, tmpbuffer, 0);
	free(tmpbuffer);
	return res;
}