glpng.c

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#ifdef _WIN32 /* Stupid Windows needs to include windows.h before gl.h */
	#undef FAR
	#include <windows.h>
#endif

#include <GL/glpng.h>
#include <GL/gl.h>
#include <stdlib.h>
#include <math.h>
#include "png/png.h"

/* Used to decide if GL/gl.h supports the paletted extension */
#ifdef GL_COLOR_INDEX1_EXT
#define SUPPORTS_PALETTE_EXT
#endif

static unsigned char DefaultAlphaCallback(unsigned char red, unsigned char green, unsigned char blue) {
	return 255;
}

static unsigned char StencilRed = 0, StencilGreen = 0, StencilBlue = 0;
static unsigned char (*AlphaCallback)(unsigned char red, unsigned char green, unsigned char blue) = DefaultAlphaCallback;
static int StandardOrientation = 0;

#ifdef SUPPORTS_PALETTE_EXT
#ifdef _WIN32
static PFNGLCOLORTABLEEXTPROC glColorTableEXT = NULL;
#endif
#endif

static int PalettedTextures = -1;
static GLint MaxTextureSize = 0;

/* screenGamma = displayGamma/viewingGamma
 * displayGamma = CRT has gamma of ~2.2
 * viewingGamma depends on platform. PC is 1.0, Mac is 1.45, SGI defaults
 * to 1.7, but this can be checked and changed w/ /usr/sbin/gamma command.
 * If the environment variable VIEWING_GAMMA is set, adjust gamma per this value.
 */
#ifdef _MAC
	static double screenGamma = 2.2 / 1.45;
#elif SGI
	static double screenGamma = 2.2 / 1.7;
#else /* PC/default */
	static double screenGamma = 2.2 / 1.0;
#endif

static char gammaExplicit = 0;	/*if  */

static void checkForGammaEnv()
{
	double viewingGamma;
	char *gammaEnv = getenv("VIEWING_GAMMA");

	if(gammaEnv && !gammaExplicit)
	{
		sscanf(gammaEnv, "%lf", &viewingGamma);
		screenGamma = 2.2/viewingGamma;
	}
}

/* Returns a safe texture size to use (ie a power of 2), based on the current texture size "i" */
static int SafeSize(int i) {
	int p;

	if (i > MaxTextureSize) return MaxTextureSize;

	for (p = 0; p < 24; p++)
		if (i <= (1<<p))
			return 1<<p;

	return MaxTextureSize;
}

/* Resize the texture since gluScaleImage doesn't work on everything */
static void Resize(int components, const png_bytep d1, int w1, int h1, png_bytep d2, int w2, int h2) {
	const float sx = (float) w1/w2, sy = (float) h1/h2;
	int x, y, xx, yy, c;
	png_bytep d;

	for (y = 0; y < h2; y++) {
		yy = (int) (y*sy)*w1;

		for (x = 0; x < w2; x++) {
			xx = (int) (x*sx);
			d = d1 + (yy+xx)*components;

			for (c = 0; c < components; c++)
				*d2++ = *d++;
		}
	}
}

static int ExtSupported(const char *x) {
	static const GLubyte *ext = NULL;
	const char *c;
	int xlen = strlen(x);

	if (ext == NULL) ext = glGetString(GL_EXTENSIONS);

	c = (const char*)ext;

	while (*c != '\0') {
		if (strcmp(c, x) == 0 && (c[xlen] == '\0' || c[xlen] == ' ')) return 1;
		c++;
	}

	return 0;
}

#define GET(o) ((int)*(data + (o)))

static int HalfSize(GLint components, GLint width, GLint height, const unsigned char *data, unsigned char *d, int filter) {
	int x, y, c;
	int line = width*components;

	if (width > 1 && height > 1) {
		if (filter)
			for (y = 0; y < height; y += 2) {
				for (x = 0; x < width; x += 2) {
					for (c = 0; c < components; c++) {
						*d++ = (GET(0)+GET(components)+GET(line)+GET(line+components)) / 4;
						data++;
					}
					data += components;
				}
				data += line;
			}
		else
			for (y = 0; y < height; y += 2) {
				for (x = 0; x < width; x += 2) {
					for (c = 0; c < components; c++) {
						*d++ = GET(0);
						data++;
					}
					data += components;
				}
				data += line;
			}
	}
	else if (width > 1 && height == 1) {
		if (filter)
			for (y = 0; y < height; y += 1) {
				for (x = 0; x < width; x += 2) {
					for (c = 0; c < components; c++) {
						*d++ = (GET(0)+GET(components)) / 2;
						data++;
					}
					data += components;
				}
			}
		else
			for (y = 0; y < height; y += 1) {
				for (x = 0; x < width; x += 2) {
					for (c = 0; c < components; c++) {
						*d++ = GET(0);
						data++;
					}
					data += components;
				}
			}
	}
	else if (width == 1 && height > 1) {
		if (filter)
			for (y = 0; y < height; y += 2) {
				for (x = 0; x < width; x += 1) {
					for (c = 0; c < components; c++) {
						*d++ = (GET(0)+GET(line)) / 2;
						data++;
					}
				}
				data += line;
			}
		else
			for (y = 0; y < height; y += 2) {
				for (x = 0; x < width; x += 1) {
					for (c = 0; c < components; c++) {
						*d++ = GET(0);
						data++;
					}
				}
				data += line;
			}
	}
	else {
		return 0;
	}

	return 1;
}

#undef GET

/* Replacement for gluBuild2DMipmaps so GLU isn't needed */
static void Build2DMipmaps(GLint components, GLint width, GLint height, GLenum format, const unsigned char *data, int filter) {
	int level = 0;
	unsigned char *d = (unsigned char *) malloc((width/2)*(height/2)*components+4);
	const unsigned char *last = data;

	glTexImage2D(GL_TEXTURE_2D, level, components, width, height, 0, format, GL_UNSIGNED_BYTE, data);
	level++;

	while (HalfSize(components, width, height, last, d, filter)) {
		if (width  > 1) width  /= 2;
		if (height > 1) height /= 2;

		glTexImage2D(GL_TEXTURE_2D, level, components, width, height, 0, format, GL_UNSIGNED_BYTE, d);
		level++;
		last = d;
	}

	free(d);
}

int APIENTRY pngLoadRaw(const char *filename, pngRawInfo *pinfo) {
	int result;
	FILE *fp = fopen(filename, "rb");
	if (fp == NULL) return 0;

	result = pngLoadRawF(fp, pinfo);

	if (fclose(fp) != 0) {
		if (result) {
			free(pinfo->Data);
			free(pinfo->Palette);
		}
		return 0;
	}

	return result;
}

int APIENTRY pngLoadRawF(FILE *fp, pngRawInfo *pinfo) {
	unsigned char header[8];
	png_structp png;
	png_infop   info;
	png_infop   endinfo;
	png_bytep   data;
   png_bytep  *row_p;
   double	fileGamma;

	png_uint_32 width, height;
	int depth, color;

	png_uint_32 i;

	if (pinfo == NULL) return 0;

	fread(header, 1, 8, fp);
	if (!png_check_sig(header, 8)) return 0;

	png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	info = png_create_info_struct(png);
	endinfo = png_create_info_struct(png);

	png_init_io(png, fp);
	png_set_sig_bytes(png, 8);
	png_read_info(png, info);
	png_get_IHDR(png, info, &width, &height, &depth, &color, NULL, NULL, NULL);

	pinfo->Width  = width;
	pinfo->Height = height;
	pinfo->Depth  = depth;

	/*--GAMMA--*/
	checkForGammaEnv();
	if (png_get_gAMA(png, info, &fileGamma))
		png_set_gamma(png, screenGamma, fileGamma);
	else
		png_set_gamma(png, screenGamma, 1.0/2.2);

	png_read_update_info(png, info);

	data = (png_bytep) malloc(png_get_rowbytes(png, info)*height);
	row_p = (png_bytep *) malloc(sizeof(png_bytep)*height);
	for (i = 0; i < height; i++)
		row_p[i] = &data[png_get_rowbytes(png, info)*i];

	png_read_image(png, row_p);
	free(row_p);

	if (color == PNG_COLOR_TYPE_PALETTE) {
		int cols;
		png_get_PLTE(png, info, (png_colorp *) &pinfo->Palette, &cols);
	}
	else {
		pinfo->Palette = NULL;
	}

	if (color&PNG_COLOR_MASK_ALPHA) {
		if (color&PNG_COLOR_MASK_PALETTE || color == PNG_COLOR_TYPE_GRAY_ALPHA)
			pinfo->Components = 2;
		else
			pinfo->Components = 4;
		pinfo->Alpha = 8;
	}
	else {
		if (color&PNG_COLOR_MASK_PALETTE || color == PNG_COLOR_TYPE_GRAY)
			pinfo->Components = 1;
		else
			pinfo->Components = 3;
		pinfo->Alpha = 0;
	}

	pinfo->Data = data;

   png_read_end(png, endinfo);
	png_destroy_read_struct(&png, &info, &endinfo);

	return 1;
}

int APIENTRY pngLoad(const char *filename, int mipmap, int trans, pngInfo *pinfo) {
	int result;
	FILE *fp = fopen(filename, "rb");
	if (fp == NULL) return 0;

	result = pngLoadF(fp, mipmap, trans, pinfo);

	if (fclose(fp) != 0) return 0;

	return result;
}

int APIENTRY pngLoadF(FILE *fp, int mipmap, int trans, pngInfo *pinfo) {
	GLint pack, unpack;
	unsigned char header[8];
	png_structp png;
	png_infop   info;
	png_infop   endinfo;
	png_bytep   data, data2;
   png_bytep  *row_p;
   double	fileGamma;