FreeType显示汉字

最新推荐文章于 2024-09-19 18:29:11 发布

转载最新推荐文章于 2024-09-19 18:29:11 发布 · 2.1k 阅读

文章标签：

#textures #keyboard #filter #function #blend #buffer

本文介绍了一个使用FreeType库结合OpenGL来渲染中文字体的示例程序。该程序能够加载并显示TrueType字体文件，如微软雅黑，并通过OpenGL纹理映射实现高质量的文字渲染效果。文章展示了如何初始化FreeType库、加载字体文件、获取字符位图并将其转换为OpenGL纹理的过程。

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#include <windows.h>
#include <stdio.h>
#include <gl/glut.h>
#include <ft2build.h>
#include FT_FREETYPE_H
#include <freetype/freetype.h>
#include <freetype/ftglyph.h>

#ifdef _WIN32
#pragma comment(lib , "libfreetype.lib")
#endif

#define MAX_NO_TEXTURES 1
#define CUBE_TEXTURE 0

GLuint texture_id[MAX_NO_TEXTURES];

struct xCharTexture
{
GLuint m_texID;
wchar_t m_chaID;
int m_Width;
int m_Height;

    int     m_adv_x;
    int     m_adv_y;
    int     m_delta_x;
    int     m_delta_y;
public:
xCharTexture()
{
  m_texID = 0;
  m_chaID = 0;
  m_Width = 0;
  m_Height = 0;
}
}g_TexID[65536];
class xFreeTypeLib
{
    FT_Library m_FT2Lib;
FT_Face    m_FT_Face;

int   m_w;
int   m_h;
public:
xFreeTypeLib()
{
  if (FT_Init_FreeType( &m_FT2Lib) )
   exit(0);
}

void load(const char* font_file , int _w , int _h)
{
  //加载一个字体,取默认的Face,一般为Regualer
  if (FT_New_Face( m_FT2Lib, font_file, 0, &m_FT_Face ))
   exit(0);
  FT_Select_Charmap(m_FT_Face, FT_ENCODING_UNICODE);
  m_w = _w ; m_h = _h;
  m_FT_Face->num_fixed_sizes;
  //大小要乘64.这是规定。照做就可以了。
  //FT_Set_Char_Size( m_FT_Face , 0 , m_w << 6, 96, 96);
  FT_Set_Pixel_Sizes(m_FT_Face,m_w, m_h);
}

GLuint loadChar(wchar_t ch)
{
if(g_TexID[ch].m_texID)
return g_TexID[ch].m_texID;

  if(FT_Load_Char(m_FT_Face, ch,FT_LOAD_RENDER|FT_LOAD_FORCE_AUTOHINT|
   (true ? FT_LOAD_TARGET_NORMAL : FT_LOAD_MONOCHROME | FT_LOAD_TARGET_MONO) )   )
  {
   return 0;
  }

        xCharTexture& charTex = g_TexID[ch];

  //得到字模
  FT_Glyph glyph;
  if(FT_Get_Glyph( m_FT_Face->glyph, &glyph ))
   return 0;

  //转化成位图
  FT_Render_Glyph( m_FT_Face->glyph,   FT_RENDER_MODE_LCD );//FT_RENDER_MODE_NORMAL );
  FT_Glyph_To_Bitmap( &glyph, ft_render_mode_normal, 0, 1 );
  FT_BitmapGlyph bitmap_glyph = (FT_BitmapGlyph)glyph;

//取道位图数据
FT_Bitmap& bitmap=bitmap_glyph->bitmap;

  //把位图数据拷贝自己定义的数据区里.这样旧可以画到需要的东西上面了。
  int width = bitmap.width;
  int height = bitmap.rows;

m_FT_Face->size->metrics.y_ppem;
m_FT_Face->glyph->metrics.horiAdvance;

  charTex.m_Width = width;
  charTex.m_Height = height;
  charTex.m_adv_x = m_FT_Face->glyph->advance.x / 64.0f;
  charTex.m_adv_y = m_FT_Face->size->metrics.y_ppem; //m_FT_Face->glyph->metrics.horiBearingY / 64.0f;
  charTex.m_delta_x = (float)bitmap_glyph->left;
  charTex.m_delta_y = (float)bitmap_glyph->top - height;

  glGenTextures(1,&charTex.m_texID);
        glBindTexture(GL_TEXTURE_2D,charTex.m_texID);
  char* pBuf = new char[width * height * 4];

bitmap.pixel_mode = FT_PIXEL_MODE_GRAY;

  for(int j=0; j < height ; j++)
  {
   for(int i=0; i < width; i++)
   {
    unsigned char _vl = (i>=bitmap.width || j>=bitmap.rows) ? 0 : bitmap.buffer[i + bitmap.width*j];
    pBuf[(4*i + (height - j - 1) * width * 4) ] = 0xff;
    pBuf[(4*i + (height - j - 1) * width * 4)+1] = 0xff;
    pBuf[(4*i + (height - j - 1) * width * 4)+2] = 0xff;
    pBuf[(4*i + (height - j - 1) * width * 4)+3] = _vl;
   }
  }

  gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGBA, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pBuf);//creates 2-D mipmaps
  //glTexImage2D( GL_TEXTURE_2D,0,GL_RGBA,width, height,0,GL_RGBA,GL_UNSIGNED_BYTE,pBuf);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_CLAMP);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_CLAMP);
  glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
  glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
  glTexEnvi(GL_TEXTURE_2D,GL_TEXTURE_ENV_MODE,GL_REPLACE);
  delete[]pBuf;
  return charTex.m_chaID;
}

}g_FreeTypeLib;

float ratio;

xCharTexture* getTextChar(wchar_t ch)
{
g_FreeTypeLib.loadChar(ch);
return &g_TexID[ch];
}

wchar_t g_UnicodeString[]=L"远交华盖欲何求，未敢翻身已碰头。/n/
破帽遮颜过闹市，漏船载酒泛中流。/n/
横眉冷对千夫指，俯首甘为孺子牛。/n/
躲进小楼成一统，管他冬夏与春秋。";

void drawText(wchar_t* _strText,int x , int y, int maxW , int h)
{
int sx = x;
int sy = y;
int maxH = h;
for(int i = 0 ; i < wcslen(_strText) ; i ++)
{

  if(_strText[i] =='/n')
  {
   sx = x ; sy += maxH + 12;
   continue;
  }
  xCharTexture* pCharTex = getTextChar(_strText[i]);
  glBindTexture(GL_TEXTURE_2D,pCharTex->m_texID);
  glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
  glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
  //glDisable(GL_TEXTURE_2D);
  int w = pCharTex->m_Width;
  int h = pCharTex->m_Height;

int ch_x = sx + pCharTex->m_delta_x;
int ch_y = sy - h - pCharTex->m_delta_y;

  if(maxH < h) maxH = h;
  glBegin ( GL_QUADS );
  {
   glTexCoord2f(0.0f, 1.0f); glVertex3f(ch_x      , ch_y    , 1.0f);
   glTexCoord2f(1.0f, 1.0f); glVertex3f(ch_x + w, ch_y    , 1.0f);
   glTexCoord2f(1.0f, 0.0f); glVertex3f(ch_x + w, ch_y + h, 1.0f);
   glTexCoord2f(0.0f, 0.0f); glVertex3f(ch_x     , ch_y + h, 1.0f);
  }
  glEnd();
  sx += pCharTex->m_adv_x;
  if(sx > x + maxW)
  {
   sx = x ; sy += maxH + 12;
  }
}
}

void init(void)
{
   glShadeModel(GL_SMOOTH);       // Enable Smooth Shading
   glClearColor(0.0f, 0.0f, 0.0f, 0.5f);    // Black Background
   glEnable ( GL_COLOR_MATERIAL );
   glColorMaterial ( GL_FRONT, GL_AMBIENT_AND_DIFFUSE );

   g_FreeTypeLib.load("simhei.ttf",24,24);

   glDisable ( GL_CULL_FACE );

glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}

void reshape( int w, int h )
{
// Prevent a divide by zero, when window is too short
// (you cant make a window of zero width).
if(h == 0)
h = 1;

ratio = 1.0f * w / h;
// Reset the coordinate system before modifying
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

// Set the viewport to be the entire window
glViewport(0, 0, w, h);
glOrtho(0,w,h,0,-100,200);
// Set the clipping volume
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0, 0, 30 ,0 , 0 ,10 , 0.0f , 1.0f , 0.0f);
}

void display( void )
{
glClearColor(0.0f , 0.0f , 0.6f , 1.0f);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

   glEnable ( GL_TEXTURE_2D );
   drawText(g_UnicodeString,50,50,900,25);
   glutSwapBuffers();
}

void keyboard ( unsigned char key, int x, int y ) // Create Keyboard Function
{
switch ( key ) {
    case 27:        // When Escape Is Pressed...
      exit ( 0 );   // Exit The Program
      break;        // Ready For Next Case
    default:        // Now Wrap It Up
      break;
}
}

void arrow_keys ( int a_keys, int x, int y ) // Create Special Function (required for arrow keys)
{
switch ( a_keys ) {
    case GLUT_KEY_UP:     // When Up Arrow Is Pressed...
      glutFullScreen ( ); // Go Into Full Screen Mode
      break;
    case GLUT_KEY_DOWN:               // When Down Arrow Is Pressed...
      glutReshapeWindow ( 500, 500 ); // Go Into A 500 By 500 Window
      break;
    default:
      break;
}
}

int main ( int argc, char** argv )   // Create Main Function For Bringing It All Together
{
glutInit            ( &argc, argv ); // Erm Just Write It =)
glutInitDisplayMode ( GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA ); // Display Mode
glutInitWindowPosition (0,0);
glutInitWindowSize ( 500, 500 ); // If glutFullScreen wasn't called this is the window size
glutCreateWindow    ( "Chinese - Display" ); // Window Title (argv[0] for current directory as title)
init ();
glutDisplayFunc     ( display ); // Matching Earlier Functions To Their Counterparts
glutReshapeFunc     ( reshape );
glutKeyboardFunc    ( keyboard );
glutSpecialFunc     ( arrow_keys );
glutIdleFunc    ( display );
glutMainLoop        ( );          // Initialize The Main Loop
return 1;
}