#include <gl/glut.h>
#include <iostream>

#include <ft2build.h>
#include FT_FREETYPE_H

using namespace std;

#define PIXEL_SIZE 20 //字体的像素大小
wchar_t ch = L'你';
FT_Library ftLibrary;
FT_Face ftFace;
GLuint  texture;

void print(GLubyte *rgba);

void ConvertMONOToRGBA(FT_Bitmap *source, GLubyte *rgba)
{
    GLubyte *s = source->buffer;
    GLubyte *t = rgba;

    for(GLuint y = source->rows; y > 0; y--)
    {
        GLubyte *ss = s;
        GLubyte *tt = t;

        for(GLuint x = source->width >> 3; x > 0; x--)
        {
            GLuint val = *ss;

            for(GLuint i = 8; i > 0; i--)
            {
                tt[0] = tt[1] = tt[2] = tt[3] = (val & (1 << (i - 1))) ? 0xFF : 0x00;
                tt += 4;
            }

            ss += 1;
        }

        GLuint rem = source->width & 7;

        if(rem > 0)
        {
            GLuint val = *ss;

            for(GLuint x = rem; x > 0; x--)
            {
                tt[0] = tt[1] = tt[2] = tt[3] = (val & 0x80) ? 0xFF : 0x00;
                tt += 4;
                val <<= 1;
            }
        }

        s += source->pitch;
        t += source->width * 4;    //pitch
    }
}

//FreeType的灰色模式：1个像素用1个字节保存。
void ConvertGRAYToRGBA(FT_Bitmap *source, GLubyte *rgba) //灰度图转RGBA
{
    for(GLuint y = 0; y < source->rows; y++)
    {
        for(GLuint x = 0; x < source->width; x++)
        {
            GLubyte *s = &source->buffer[(y * source->pitch) + x];
            GLubyte *t = &rgba[((y * source->pitch) + x) * 4];

            t[0] = t[1] = t[2] = 0xFF; //RGB为255
            t[3] = *s; //A通道存灰度图
        }
    }
}

GLubyte* get_rgba(FT_Bitmap& bitmap)
{
    int rgbaSize = bitmap.rows * bitmap.rows * 4;
    GLubyte *rgba = new GLubyte[rgbaSize];

    switch(bitmap.pixel_mode)     //像素模式
    {
    case FT_PIXEL_MODE_MONO: //黑白
    {
        // 将黑白转成RGBA
        ConvertMONOToRGBA(&bitmap, rgba);
        break;
    }

    case FT_PIXEL_MODE_GRAY: //灰度
    {
        ConvertGRAYToRGBA(&bitmap, rgba); //灰度转RGBA
        break;
    }

    default:
    {
        memset(rgba, 0xFF, rgbaSize);
        break;
    }

    }

    return rgba;
}

GLubyte* get_rgba_2(FT_Bitmap& bitmap) //自己写的，对位图的理解有不足
{
    int rgbaSize = bitmap.rows * bitmap.rows * 4;
    GLubyte *rgba = new GLubyte[rgbaSize];

    for(GLuint y = 0; y < bitmap.rows; y++)
    {
        for(GLuint x = 0; x < bitmap.width; x++)
        {
            GLubyte *s = &bitmap.buffer[y * bitmap.pitch + x / 8];
            GLubyte *t = &rgba[((y * bitmap.width) + x) * 4];

            if((*s & (0xC0 >> (x % 8))) == 0)  //非字符像素
            {
                t[0] = t[1] = t[2] = t[3] = 0x00;
            }
            else //字符像素
            {
                t[0] = t[1] = t[2] = t[3] = 0xff;
            }
        }
    }

    return rgba;
}

void init()
{
    #pragma region FreeType的设置
    // - 初始化FreeType对象
    FT_Init_FreeType(&ftLibrary);

    FT_New_Face(ftLibrary,
                "C:\\WINDOWS\\Fonts\\simhei.ttf", //黑体中文字库
                0,
                &ftFace);

    // - 设置
    FT_Set_Pixel_Sizes(ftFace, PIXEL_SIZE, 0); //像素大小

    // - 得到字符码的字形索引
    FT_UInt uiGlyphIndex = FT_Get_Char_Index(ftFace, ch);

    if(uiGlyphIndex <= 0)
    {
        printf("未找到该字符的索引");
    }

    FT_Load_Glyph(ftFace, uiGlyphIndex, FT_LOAD_DEFAULT);
    #pragma endregion


    #pragma region 生成位图

    // - 生成位图：FreeType所得是8位的灰度图
    if(ftFace->glyph->format != FT_GLYPH_FORMAT_BITMAP)
    {
        FT_Render_Glyph(ftFace->glyph, FT_RENDER_MODE_MONO);
    }

    // - 查看位图信息
    printf("行：%d;列：%d\n", ftFace->glyph->bitmap.rows, ftFace->glyph->bitmap.width);
    printf("\n------ 位图信息 ------\n");

    for(int iRow = 0; iRow < ftFace->glyph->bitmap.rows; iRow++)
    {
        for(int iCol = 0; iCol < ftFace->glyph->bitmap.width; iCol++)
        {
            printf("%d\t", ftFace->glyph->bitmap.buffer[iRow * ftFace->glyph->bitmap.pitch + iCol / 8]);
        }

        printf("\n");
    }

    #pragma endregion

    #pragma region 打印成字体
    printf("\n------ 查看字体信息 ------\n");

    for(int iRow = 0; iRow < ftFace->glyph->bitmap.rows; iRow++)
    {
        for(int iCol = 0; iCol < ftFace->glyph->bitmap.width; iCol++)
        {
            auto index = iRow * ftFace->glyph->bitmap.pitch + iCol / 8;
            auto tmp = 0xC0 >> (iCol % 8);
            auto value = index & tmp;

            if((ftFace->glyph->bitmap.buffer[iRow * ftFace->glyph->bitmap.pitch + iCol / 8] & (0xC0 >> (iCol % 8))) == 0)
            {
                printf(" ");
            }
            else
            {
                printf("1");
            }
        }

        printf("\n");
    }

    #pragma endregion

    #pragma region 生成纹理
    // 生成纹理
    glEnable(GL_TEXTURE_2D);
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);

    GLubyte* rgba = get_rgba(ftFace->glyph->bitmap);
    //GLubyte* rgba = get_rgba_2(ftFace->glyph->bitmap);

    print(rgba);
    glTexImage2D(GL_TEXTURE_2D,
                 0,
                 GL_RGBA,
                 ftFace->glyph->bitmap.width, ftFace->glyph->bitmap.rows,
                 0,
                 GL_RGBA,
                 GL_UNSIGNED_BYTE,
                 rgba);
    delete rgba;

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    glBindTexture(GL_TEXTURE_2D, 0); //解绑
    #pragma endregion

    // 清空资源
    FT_Done_Face(ftFace);
    FT_Done_FreeType(ftLibrary);
}

void myDisplay(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glClearColor(0, 0, 0, 0);

    // 画纹理
    glBindTexture(GL_TEXTURE_2D, texture);
    glBegin(GL_QUADS);
    // 要注意字体纹理和OpenGL的绘制关系
    glTexCoord2d(0, 0);         //纹理 左下角
    glVertex2f(-0.8f, 0.8f);    //OpenGL 左上角

    glTexCoord2d(0, 1);         //左上角
    glVertex2f(-0.8f, -0.8f);   //左下角

    glTexCoord2f(1.0f, 1.0f);   //右上角
    glVertex2f(0.8f, -0.8f);    //右下角

    glTexCoord2d(1, 0);         //右下角
    glVertex2f(0.8f, 0.8f);     //右上角

    glEnd();
    glFlush();
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);                          //初始化GLUT
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);    //初始化显示模式
    glutInitWindowPosition(100, 100);               //窗体位置
    glutInitWindowSize(500, 500);                   //窗体大小
    glutCreateWindow("OpenGL One Char");            //传入窗口名称，并开窗

    init();
    glutDisplayFunc(&myDisplay);                    //绘制的回调函数

    glutMainLoop();                                 //循环绘制
    return 0;
}

void print(GLubyte *rgba) //打印RGBA
{
    printf("\n----- R -----\n");

    for(GLuint y = 0; y < ftFace->glyph->bitmap.rows; y++)
    {
        for(GLuint x = 0; x < ftFace->glyph->bitmap.width; x++)
        {
            GLubyte *s = &ftFace->glyph->bitmap.buffer[(y * ftFace->glyph->bitmap.pitch) + x];
            GLubyte *t = &rgba[((y * ftFace->glyph->bitmap.pitch) + x) * 4];

            printf("%d\t", t[0]);
        }

        printf("\n");
    }

    printf("\n----- G -----\n");

    for(GLuint y = 0; y < ftFace->glyph->bitmap.rows; y++)
    {
        for(GLuint x = 0; x < ftFace->glyph->bitmap.width; x++)
        {
            GLubyte *s = &ftFace->glyph->bitmap.buffer[(y * ftFace->glyph->bitmap.pitch) + x];
            GLubyte *t = &rgba[((y * ftFace->glyph->bitmap.pitch) + x) * 4];

            printf("%d\t", t[1]);
        }

        printf("\n");
    }

    printf("\n----- B -----\n");

    for(GLuint y = 0; y < ftFace->glyph->bitmap.rows; y++)
    {
        for(GLuint x = 0; x < ftFace->glyph->bitmap.width; x++)
        {
            GLubyte *s = &ftFace->glyph->bitmap.buffer[(y * ftFace->glyph->bitmap.pitch) + x];
            GLubyte *t = &rgba[((y * ftFace->glyph->bitmap.pitch) + x) * 4];

            printf("%d\t", t[2]);
        }

        printf("\n");
    }

    printf("\n----- A -----\n");

    for(GLuint y = 0; y < ftFace->glyph->bitmap.rows; y++)
    {
        for(GLuint x = 0; x < ftFace->glyph->bitmap.width; x++)
        {
            GLubyte *s = &ftFace->glyph->bitmap.buffer[(y * ftFace->glyph->bitmap.pitch) + x];
            GLubyte *t = &rgba[((y * ftFace->glyph->bitmap.pitch) + x) * 4];

            printf("%d\t", t[3]);
        }

        printf("\n");
    }
}