在2440开发板液晶上显示两行字

用到了freetype库

下面是测试代码：

/* example1.c                                                      */
/*                                                                 */
/* This small program shows how to print a rotated string with the */
/* FreeType 2 library.                                             */


#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <linux/fb.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <wchar.h>

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_GLYPH_H


//#define WIDTH   var.xres//80
//#define HEIGHT  var.yres//80
//
//
///* origin is the upper left corner */
//unsigned char image[HEIGHT][WIDTH];

int fd_fb;
struct fb_var_screeninfo var;	/* Current var */
struct fb_fix_screeninfo fix;	/* Current fix */
int screen_size;
unsigned char *fbmem;
unsigned int line_width;
unsigned int pixel_width;



/* color : 0x00RRGGBB */
void lcd_put_pixel(int x, int y, unsigned int color)
{
	unsigned char *pen_8 = fbmem+y*line_width+x*pixel_width;
	unsigned short *pen_16;	
	unsigned int *pen_32;	

	unsigned int red, green, blue;	

	pen_16 = (unsigned short *)pen_8;
	pen_32 = (unsigned int *)pen_8;

	switch (var.bits_per_pixel)
	{
		case 8:
		{
			*pen_8 = color;
			break;
		}
		case 16:
		{
			/* 565 */
			red   = (color >> 16) & 0xff;
			green = (color >> 8) & 0xff;
			blue  = (color >> 0) & 0xff;
			color = ((red >> 3) << 11) | ((green >> 2) << 5) | (blue >> 3);
			*pen_16 = color;
			break;
		}
		case 32:
		{
			*pen_32 = color;
			break;
		}
		default:
		{
			printf("can't surport %dbpp\n", var.bits_per_pixel);
			break;
		}
	}
}

/* Replace this function with something useful. */

void
draw_bitmap( FT_Bitmap*  bitmap,
             FT_Int      x,
             FT_Int      y)
{
  FT_Int  i, j, p, q;
  FT_Int  x_max = x + bitmap->width;
  FT_Int  y_max = y + bitmap->rows;


	//printf("x = %d, y = %d\n", x, y);

  for ( i = x, p = 0; i < x_max; i++, p++ )
  {
    for ( j = y, q = 0; j < y_max; j++, q++ )
    {
      if ( i < 0      || j < 0       ||
           i >= var.xres || j >= var.yres )
        continue;

//      image[j][i] |= bitmap->buffer[q * bitmap->width + p];
		lcd_put_pixel(i, j, bitmap->buffer[q * bitmap->width + p]);
    }
  }
}

int
main( int     argc,
      char**  argv )
{
  FT_Library    library;
  FT_Face       face;

  FT_GlyphSlot  slot;
  FT_Matrix     matrix;                 /* transformation matrix */
  FT_Vector     pen;                    /* untransformed origin  */
  FT_Error      error;

  char*         filename;
//  char*         text;

  double        angle;
  int           n;

 int bbox_ymax=0,bbox_ymin=1000;
	FT_BBox bbox;
	FT_Glyph  glyph;
 
  wchar_t *chinese_str = L"朋哥哥gif";
  
  wchar_t *chinese_str1 = L"无敌朋哥";

  if ( argc != 2 )
  {
    fprintf ( stderr, "usage: %s font\n", argv[0] );
    exit( 1 );
  }
  
  
  	fd_fb = open("/dev/fb0", O_RDWR);
	if (fd_fb < 0)
	{
		printf("can't open /dev/fb0\n");
		return -1;
	}

	if (ioctl(fd_fb, FBIOGET_VSCREENINFO, &var))
	{
		printf("can't get var\n");
		return -1;
	}

	if (ioctl(fd_fb, FBIOGET_FSCREENINFO, &fix))
	{
		printf("can't get fix\n");
		return -1;
	}

	line_width  = var.xres * var.bits_per_pixel / 8;
	pixel_width = var.bits_per_pixel / 8;
	screen_size = var.xres * var.yres * var.bits_per_pixel / 8;
	fbmem = (unsigned char *)mmap(NULL , screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);
	if (fbmem == (unsigned char *)-1)
	{
		printf("can't mmap\n");
		return -1;
	}
	

  filename      = argv[1];                           /* first argument     */
  //text          = argv[2];                           /* second argument    */
  //num_chars     = strlen( text );
  angle         = ( 0.0 / 360 ) * 3.14159 * 2;      /* use 25 degrees     */
//  target_height = HEIGHT;

  error = FT_Init_FreeType( &library );              /* initialize library */
  /* error handling omitted */

  error = FT_New_Face( library, argv[1], 0, &face ); /* create face object */
  /* error handling omitted */

#if 0
  /* use 50pt at 100dpi */
  error = FT_Set_Char_Size( face, 50 * 64, 0,
                            100, 0 );                /* set character size */

	/* pixels = 50 /72 * 100 = 69  */
#else
	FT_Set_Pixel_Sizes(face, 24, 0);
#endif
  /* error handling omitted */

  slot = face->glyph;

  /* set up matrix */
  matrix.xx = (FT_Fixed)( cos( angle ) * 0x10000L );
  matrix.xy = (FT_Fixed)(-sin( angle ) * 0x10000L );
  matrix.yx = (FT_Fixed)( sin( angle ) * 0x10000L );
  matrix.yy = (FT_Fixed)( cos( angle ) * 0x10000L );


	/* 清屏: 全部设为黑色 */
	memset(fbmem, 0, screen_size);
	
  /* the pen position in 26.6 cartesian space coordinates; */
  /* start at (100,100) relative to the upper left corner  */
  pen.x = 100 * 64;
  pen.y = ( var.yres - 100 ) * 64;

  for ( n = 0; n < wcslen(chinese_str); n++ )
  {
    /* set transformation */
    FT_Set_Transform( face, &matrix, &pen );

    /* load glyph image into the slot (erase previous one) */
    error = FT_Load_Char( face, chinese_str[n], FT_LOAD_RENDER );
    if ( error )
      continue;                 /* ignore errors */

    error = FT_Get_Glyph( face->glyph, &glyph );
		if (error)
		{
			printf("FT_Get_Glyph error!\n");
			return -1;
		}

    FT_Glyph_Get_CBox(glyph, FT_GLYPH_BBOX_TRUNCATE, &bbox );
    
    if(bbox_ymax < bbox.yMax)
    	bbox_ymax =bbox.yMax;
    if(bbox_ymin > bbox.yMin)
    	bbox_ymin =bbox.yMin;

    /* now, draw to our target surface (convert position) */
    draw_bitmap( &slot->bitmap,
                 slot->bitmap_left,
                 var.yres - slot->bitmap_top );


    /* increment pen position */
    pen.x += slot->advance.x;
//    pen.y += slot->advance.y;
  }
  
  printf("the second line\n");
  printf("the line_box_ymax = %d ,line_box_ymin = %d \n",bbox_ymax,bbox_ymin);
    /* the pen position in 26.6 cartesian space coordinates; */
  /* start at (100,100) relative to the upper left corner  */
  pen.x = 100 * 64;
  pen.y = ( var.yres - (bbox_ymax-bbox_ymin+100) ) * 64;

  for ( n = 0; n < wcslen(chinese_str1); n++ )
  {
    /* set transformation */
    FT_Set_Transform( face, &matrix, &pen );

    /* load glyph image into the slot (erase previous one) */
    error = FT_Load_Char( face, chinese_str1[n], FT_LOAD_RENDER );
    if ( error )
      continue;                 /* ignore errors */

    error = FT_Get_Glyph( face->glyph, &glyph );
		if (error)
		{
			printf("FT_Get_Glyph error!\n");
			return -1;
		}

    FT_Glyph_Get_CBox(glyph, FT_GLYPH_BBOX_TRUNCATE, &bbox );
    
    if(bbox_ymax < bbox.yMax)
    	bbox_ymax =bbox.yMax;
    if(bbox_ymin > bbox.yMin)
    	bbox_ymin =bbox.yMin;

    /* now, draw to our target surface (convert position) */
    draw_bitmap( &slot->bitmap,
                 slot->bitmap_left,
                 var.yres - slot->bitmap_top );


    /* increment pen position */
    pen.x += slot->advance.x;
//    pen.y += slot->advance.y;
  }
  
  FT_Done_Face    ( face );
  FT_Done_FreeType( library );

printf("the end\n");
  return 0;
}

/* EOF */

交叉编译：

arm-linux-gcc -o mycode1 mycode1.c -lfreetype -lm -Wall -finput-charset=GBK

注意代码中 ，下面这两个变量定义后，一定要记得初始化。

int bbox_ymax=0,bbox_ymin=1000;

若不初始化，写成  int  bbox_ymax , bbox_ymin ;

则第二行显示不出字，添加打印程序后才发现错误。

/mnt # ./mycode1 ./simsun.ttc 
the second line
the line_box_ymax = 191 ,line_box_ymin = -1224855552 
the end

 由上面打印信息，很明显看出来 line_box_ymin = -1224855552 ，是变量没有初始化的问题。