/* PNG loader library for OpenGL v1.45 (10/07/00)
 * by Ben Wyatt ben@wyatt100.freeserve.co.uk
 * Using LibPNG 1.0.2 and ZLib 1.1.3
 *
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the author be held liable for any damages arising from the
 * use of this software.
 *
 * Permission is hereby granted to use, copy, modify, and distribute this
 * source code, or portions hereof, for any purpose, without fee, subject to
 * the following restrictions:
 *
 * 1. The origin of this source code must not be misrepresented. You must not
 *    claim that you wrote the original software. If you use this software in
 *    a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered versions must be plainly marked as such and must not be
 *    misrepresented as being the original source.
 * 3. This notice must not be removed or altered from any source distribution.
 *
 * ---------------------------------------------------
 * This version has been modified for usage inside ARB
 * http://arb-home.de/
 */

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

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

#if 0
#define GLPNG_CHECK_SIG(header,size) png_check_sig(header,size) // old libpng
#else
#define GLPNG_CHECK_SIG(header,size) (png_sig_cmp(header,0,size)==0)
#endif

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

#pragma GCC diagnostic ignored "-Wunused-parameter"
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,
 * 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;
#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++;
        }
    }
}

#ifdef SUPPORTS_PALETTE_EXT
#ifdef _WIN32
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;
}
#endif
#endif

#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);
}

static int APIENTRY pngLoadF(FILE *fp, int mipmap, int trans, pngInfo *pinfo) {
    unsigned char header[8];
    
    if (fread(header, 1, 8, fp) != 8) return 0;
    if (!GLPNG_CHECK_SIG(header, 8)) return 0;

    GLint        pack, unpack;
    png_structp  png;
    png_infop    info;
    png_infop    endinfo;
    png_bytep    data;
    png_bytep   *row_p;
    double       fileGamma;

    png_uint_32 width, height, rw, rh;
    int depth, color;

    png_uint_32 i;

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

    // DH: added following lines
    if (setjmp(png_jmpbuf(png))) {
        png_destroy_read_struct(&png, &info, &endinfo);
        return 0;
    }
    // ~DH

    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);

    if (pinfo != NULL) {
        pinfo->Width  = width;
        pinfo->Height = height;
        pinfo->Depth  = depth;
    }

    if (MaxTextureSize == 0)
        glGetIntegerv(GL_MAX_TEXTURE_SIZE, &MaxTextureSize);

#ifdef SUPPORTS_PALETTE_EXT
#ifdef _WIN32
    if (PalettedTextures == -1)
        PalettedTextures = ExtSupported("GL_EXT_paletted_texture") && (strstr((const char *) glGetString(GL_VERSION), "1.1.0 3Dfx Beta") == NULL);

    if (PalettedTextures) {
        if (glColorTableEXT == NULL) {
            glColorTableEXT = (PFNGLCOLORTABLEEXTPROC) wglGetProcAddress("glColorTableEXT");
            if (glColorTableEXT == NULL)
                PalettedTextures = 0;
        }
    }
#endif
#endif

    if (PalettedTextures == -1)
        PalettedTextures = 0;

    if (color == PNG_COLOR_TYPE_GRAY || color == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png);

    if (color&PNG_COLOR_MASK_ALPHA && trans != GLPNG_ALPHA) {
        png_set_strip_alpha(png);
        color &= ~PNG_COLOR_MASK_ALPHA;
    }

    if (!(PalettedTextures && mipmap >= 0 && trans == GLPNG_SOLID))
        if (color == PNG_COLOR_TYPE_PALETTE)
            png_set_expand(png);

    // --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++) {
        if (StandardOrientation)
            row_p[height - 1 - i] = &data[png_get_rowbytes(png, info)*i];
        else
            row_p[i] = &data[png_get_rowbytes(png, info)*i];
    }

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

    rw = SafeSize(width), rh = SafeSize(height);

    if (rw != width || rh != height) {
        const int channels = png_get_rowbytes(png, info)/width;

        png_bytep data2 = (png_bytep) malloc(rw*rh*channels);

        // Doesn't work on certain sizes
        /*              if (gluScaleImage(glformat, width, height, GL_UNSIGNED_BYTE, data, rw, rh, GL_UNSIGNED_BYTE, data2) != 0)
                        return 0;
        */
        Resize(channels, data, width, height, data2, rw, rh);

        width = rw, height = rh;
        free(data);
        data  = data2;
    }

    { // OpenGL stuff
        glGetIntegerv(GL_PACK_ALIGNMENT, &pack);
        glGetIntegerv(GL_UNPACK_ALIGNMENT, &unpack);
        glPixelStorei(GL_PACK_ALIGNMENT, 1);
        glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

#ifdef SUPPORTS_PALETTE_EXT
        if (PalettedTextures && mipmap >= 0 && trans == GLPNG_SOLID && color == PNG_COLOR_TYPE_PALETTE) {
            png_colorp pal;
            int cols;
            GLint internalFormat;

            if (pinfo != NULL) pinfo->Alpha = 0;
            png_get_PLTE(png, info, &pal, &cols);

            switch (cols) {
                case 1<<1:  internalFormat = GL_COLOR_INDEX1_EXT;  break;
                case 1<<2:  internalFormat = GL_COLOR_INDEX2_EXT;  break;
                case 1<<4:  internalFormat = GL_COLOR_INDEX4_EXT;  break;
                case 1<<8:  internalFormat = GL_COLOR_INDEX8_EXT;  break;
                case 1<<12: internalFormat = GL_COLOR_INDEX12_EXT; break;
                case 1<<16: internalFormat = GL_COLOR_INDEX16_EXT; break;
                default:
                    return 0;
            }
            glColorTableEXT(GL_TEXTURE_2D, GL_RGB8, cols, GL_RGB, GL_UNSIGNED_BYTE, pal);
            glTexImage2D(GL_TEXTURE_2D, mipmap, internalFormat, width, height, 0, GL_COLOR_INDEX, GL_UNSIGNED_BYTE, data);
        }
        else
#endif
            if (trans == GLPNG_SOLID || trans == GLPNG_ALPHA || color == PNG_COLOR_TYPE_RGB_ALPHA || color == PNG_COLOR_TYPE_GRAY_ALPHA) {
                GLenum glformat;
                GLint glcomponent;

                switch (color) {
                    case PNG_COLOR_TYPE_GRAY:
                    case PNG_COLOR_TYPE_RGB:
                    case PNG_COLOR_TYPE_PALETTE:
                        glformat = GL_RGB;
                        glcomponent = 3;
                        if (pinfo != NULL) pinfo->Alpha = 0;
                        break;

                    case PNG_COLOR_TYPE_GRAY_ALPHA:
                    case PNG_COLOR_TYPE_RGB_ALPHA:
                        glformat = GL_RGBA;
                        glcomponent = 4;
                        if (pinfo != NULL) pinfo->Alpha = 8;
                        break;

                    default:
                        return 0;
                }

                if (mipmap == GLPNG_BUILDMIPMAPS)
                    Build2DMipmaps(glcomponent, width, height, glformat, data, 1);
                else if (mipmap == GLPNG_SIMPLEMIPMAPS)
                    Build2DMipmaps(glcomponent, width, height, glformat, data, 0);
                else
                    glTexImage2D(GL_TEXTURE_2D, mipmap, glcomponent, width, height, 0, glformat, GL_UNSIGNED_BYTE, data);
            }
            else {
                png_bytep p, endp, q, data2;
                int r, g, b, a;

                p = data, endp = p+width*height*3;
                q = data2 = (png_bytep) malloc(sizeof(png_byte)*width*height*4);

                if (pinfo != NULL) pinfo->Alpha = 8;

#define FORSTART                                \
                do {                            \
                    r = *p++; /* red  */        \
                    g = *p++; /* green */       \
                    b = *p++; /* blue */        \
                    *q++ = r;                   \
                    *q++ = g;                   \
                    *q++ = b;

#define FOREND                                  \
                q++;                            \
            } while (p != endp);

#define ALPHA *q

                switch (trans) {
                    case GLPNG_CALLBACK:
                        FORSTART
                            ALPHA = AlphaCallback((unsigned char) r, (unsigned char) g, (unsigned char) b);
                        FOREND
                            break;

                    case GLPNG_STENCIL:
                        FORSTART
                            if (r == StencilRed && g == StencilGreen && b == StencilBlue)
                                ALPHA = 0;
                            else
                                ALPHA = 255;
                        FOREND
                            break;

                    case GLPNG_BLEND1:
                        FORSTART
                            a = r+g+b;
                        if (a > 255) ALPHA = 255; else ALPHA = a;
                        FOREND
                            break;

                    case GLPNG_BLEND2:
                        FORSTART
                            a = r+g+b;
                        if (a > 255*2) ALPHA = 255; else ALPHA = a/2;
                        FOREND
                            break;

                    case GLPNG_BLEND3:
                        FORSTART
                            ALPHA = (r+g+b)/3;
                        FOREND
                            break;

                    case GLPNG_BLEND4:
                        FORSTART
                            a = r*r+g*g+b*b;
                        if (a > 255) ALPHA = 255; else ALPHA = a;
                        FOREND
                            break;

                    case GLPNG_BLEND5:
                        FORSTART
                            a = r*r+g*g+b*b;
                        if (a > 255*2) ALPHA = 255; else ALPHA = a/2;
                        FOREND
                            break;

                    case GLPNG_BLEND6:
                        FORSTART
                            a = r*r+g*g+b*b;
                        if (a > 255*3) ALPHA = 255; else ALPHA = a/3;
                        FOREND
                            break;

                    case GLPNG_BLEND7:
                        FORSTART
                            a = r*r+g*g+b*b;
                        if (a > 255*255) ALPHA = 255; else ALPHA = (int) sqrt(a);
                        FOREND
                            break;
                }

#undef FORSTART
#undef FOREND
#undef ALPHA

                if (mipmap == GLPNG_BUILDMIPMAPS)
                    Build2DMipmaps(4, width, height, GL_RGBA, data2, 1);
                else if (mipmap == GLPNG_SIMPLEMIPMAPS)
                    Build2DMipmaps(4, width, height, GL_RGBA, data2, 0);
                else
                    glTexImage2D(GL_TEXTURE_2D, mipmap, 4, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data2);

                free(data2);
            }

        glPixelStorei(GL_PACK_ALIGNMENT, pack);
        glPixelStorei(GL_UNPACK_ALIGNMENT, unpack);
    } // OpenGL end

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

    free(data);

    return 1;
}

static 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;
}

static unsigned int SetParams(int wrapst, int magfilter, int minfilter) {
    unsigned int id;

    glGenTextures(1, &id);
    glBindTexture(GL_TEXTURE_2D, id);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapst);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapst);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magfilter);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minfilter);

    return id;
}

unsigned int APIENTRY pngBind(const char *filename, int mipmap, int trans, pngInfo *info, int wrapst, int minfilter, int magfilter) {
    unsigned int id = SetParams(wrapst, magfilter, minfilter);

    if (id != 0 && pngLoad(filename, mipmap, trans, info))
        return id;
    return 0;
}

