4.数码相框-freetype多行显示,居中显示

本章主要内容如下:

• 1)多行显示
• 2)居中显示

---

在上章3.数码相框-通过freetype库实现矢量显示里,我们使用矢量坐标时,该坐标仅仅在原点位置处,所以文字有可能会超出坐标,如下图所示:

 

既然超出了坐标,会不会被下一行的文字覆盖掉?

答:对于几行同样大的文字而言,不会的.

以 24*24的韦字为例,让它显示在(0,40)处,所以文字的y范围在17~40,如下图所示,发现该文字超过了原点,而上方数据又会空出来一段,就不会覆盖到上一行数据.

 

 对于几行规格大小不同的文字,则有可能会被覆盖.以20*20的韦字为例,如下图,可以发现空出的数据比24*24的少1行,若上一行的规格很大时(超出原点很大一部分), 那么这个20*20的韦字,就会覆盖掉上一行文字底部的数据.

 

 

1.从左显示多行24*24文字

内容如下:

定义一个两个标志变量line_box_ymax和line_box_ymin.

通过FT_Glyph_Get_CBox()测量字形图像,获取一行文字的yMax,Min最大值,最小值.

显示第一行时:

pen.x = 0* 64;
pen.y = ( fb_var.yres-24 ) * 64;   // fb_var.yres:LCD总高度,   原点为(0,24)

显示第2~n行时:

pen.x = 0* 64;
pen.y-= (line_box_ymax - line_box_ymin )* 64;   //在上行的pen.y基础上,减去上行的边框高

  

代码如下:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <string.h>
#include <linux/fb.h>
#include <math.h>
#include<wchar.h>
#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_GLYPH_H

unsigned char *fbmem;
unsigned char *hzkmem;

struct fb_var_screeninfo fb_var;
struct fb_fix_screeninfo  fb_fix;

unsigned int screensize;
#define FONTDATAMAX 4096

/*rgb565*/
void pixel_show(int x,int y, unsigned int color)
{
       unsigned int red,green,blue;
       switch(fb_var.bits_per_pixel)        //rgb   像素
       {
            case 32:
            {
                unsigned int  *addr=(unsigned int  *)fbmem+(fb_var.xres*y+x);
                *addr=color;   
                 break;
            }
            case 24:
           {
                unsigned int  *addr=(unsigned int  *)fbmem+(fb_var.xres*y+x);
                *addr=color;
                 break;
           }
           case 16:            //将RGB888 转为RGB565
           {
                unsigned short  *addr=(unsigned short  *)fbmem+(fb_var.xres*y+x);
                red   = (color >> 16) & 0xff;
                green = (color >> 8) & 0xff;
                blue  = (color >> 0) & 0xff;
                color = ((red >> 3) << 11) | ((green >> 2) << 5) | (blue >> 3);
                *addr = color;
                break;
           }
           case 8:
          {
               unsigned char  *addr=(unsigned char  *)fbmem+(fb_var.xres*y+x);     
               *addr = (unsigned char)color;
               break;
          }
          default:
         {
            printf("can't  surport %dbpp 
",fb_var.bits_per_pixel);
            break;
         }
       }
}

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;        //x:当前X位置， bitmap->该字宽度
  FT_Int  y_max = y + bitmap->rows;

  for ( i = x, p = 0; i < x_max; i++, p++ )   //i:lcd的x轴
  {
    for ( j = y, q = 0; j < y_max; j++, q++ )  //j:lcd的y轴
    {
      if ( i < 0      || j < 0       ||
           i >= fb_var.xres || j >= fb_var.yres )
        continue;

        pixel_show( i, j,  bitmap->buffer[q * bitmap->width + p]);
    }
  }
} 

unsigned int line_box_ymax=0;
unsigned int line_box_ymin=30000;

void lcd_vector_show(char *argv,wchar_t  *str[],unsigned int lines)
{
   FT_Glyph  glyph;
   FT_BBox   acbox;
   FT_Library    library;
   FT_Face       face;
   FT_GlyphSlot  slot;
   FT_Vector     pen;                    /* untransformed origin  */
   unsigned char error;
   unsigned int line_nums=0;              
   unsigned char  n,font_size;

   error = FT_Init_FreeType( &library );              /* initialize library */
      if(error)
       {
            printf("FT_Init_FreeType ERROR
");
            return ;
        }

     error = FT_New_Face( library, argv, 0, &face ); /* create face object */
     if(error)
        {
            printf("FT_New_Face ERROR
");
            return ;
        }
     slot = face->glyph;

     error = FT_Set_Pixel_Sizes( face, 0,24);     /* set character size */

     for(line_nums=0;line_nums<lines;line_nums++)
   {
    /*设置笔记落下位置*/
    /*显示坐标(从LCD左上方显示3  行)
      *x=0
      *y=fb_var.yres-24   (减24,是因为笛卡尔坐标以左下方开始计算坐标值的)
      */
     if(line_nums==0)
     {
       pen.x = 0* 64;
       pen.y = ( fb_var.yres-24 ) * 64;  
     }
     else
    {
       pen.x = 0* 64;
       pen.y-= (line_box_ymax - line_box_ymin )* 64;   //在上行的Y值上减去边框高
       /*清空标志位,因为上一行的ymin永远当前行小*/
       line_box_ymax=0;
       line_box_ymin=30000;
    }
     for ( n = 0; n < wcslen(str[line_nums]); n++ )
  {   
    FT_Set_Transform( face, 0, &pen );
    error = FT_Load_Char( face,str[line_nums][n], FT_LOAD_RENDER );
      if ( error )
         {
         printf("FT_Load_Char ERROR
"); 
         continue; 
        }
        FT_Get_Glyph( face->glyph, &glyph );                   //获取字形图像 的信息
        FT_Glyph_Get_CBox(  glyph,FT_GLYPH_BBOX_TRUNCATE,&acbox );     //获取此行文字的box

        if(acbox.yMax>acbox.yMin)
       {
       if(line_box_ymax<acbox.yMax)
            line_box_ymax=acbox.yMax;
        if(line_box_ymin>acbox.yMin)
            line_box_ymin=acbox.yMin;
       }
        draw_bitmap( &slot->bitmap,
                 slot->bitmap_left,
                 fb_var.yres- slot->bitmap_top );
      pen.x += slot->advance.x;

   }
 }
     FT_Done_Face( face );
     FT_Done_FreeType( library ); 
}

int main(int argc,char **argv)
{
    int fd_fb,fd_hzk;
    struct stat  hzk_start;             //HZK16文件信息

    wchar_t   *chinese_str[]={L"韦东山gh",L"abc 中国chinese",L"哈哈哈哈wqe"};  

    if ( argc != 2 )
    {
      printf ("usage: %s  font_file 
", argv[0] );
      return 0;
     }

    fd_fb=open("/dev/fb0", O_RDWR);
    if(fd_fb<0)
    {
        printf("can't open /dev/fb0 
");
        return 0;
     }

    if(ioctl(fd_fb,FBIOGET_VSCREENINFO,&fb_var)<0)
    {
        printf("can't get var 
");
        return 0;
    }

   if(ioctl(fd_fb,FBIOGET_FSCREENINFO,&fb_fix)<0)
    {
        printf("can't get fix 
");
        return 0;
    }

    screensize=fb_var.xres*fb_var.yres*(fb_var.bits_per_pixel/8);       //显存大小

    fbmem =(unsigned char *)mmap(NULL,screensize, PROT_READ|PROT_WRITE,MAP_SHARED,
                  fd_fb, 0);                       //映射fb0

    if(!fbmem)
    {
        printf("can't map /dev/fb0 
");
        return 0;
    }

    memset(fbmem, 0, screensize);            //清屏黑色

    /*显示3  行 矢量文字*/
    lcd_vector_show(argv[1], chinese_str,3);  

    munmap(fbmem,screensize);
    return 0;
}

2.居中显示

参考第11页:https://wenku.baidu.com/view/060a0b44f12d2af90342e63a.html?from=search

1)首先定义一个用来存储一行文字的字形图像数组

#define MAX_GLYPHS  100       //最多存储一行100个字

TGlyph glyphs[MAX_GLYPHS]; /* glyphs table */

2)首先以坐标(0,0)为基值,获取每个文字的字形图像和坐标值,存到glyphs[]里

/*初始化库,获取face,设置字体*/
error = FT_Init_FreeType( &library );              /* initialize library */
if(error)
{ //... ...}
error = FT_New_Face( library, argv[1], 0, &face ); /* create face object */
if(error)
{//... ...}
FT_Set_Pixel_Sizes(face, 24, 0);

... ...
 
int num_glyphs = 0;
PGlyph glyph = glyphs;         // Pglyph在库里被定义为Tglyph *, glyph指向glyphs
int pen_x = 0;
int pen_y = 0;

for (n = 0; n < wcslen(wstr); n++)              // wstr:  wchar_t类型的文字数组
{
glyph->index = FT_Get_Char_Index( face, wstr[n]);    //存储每个文字的索引值


glyph->pos.x = pen_x;          //记录每个文字的坐标值,后面会用来设置字形图像的位置信息
glyph->pos.y = pen_y;        

error=FT_Load_Glyph(face, glyph->index, FT_LOAD_DEFAULT); 
//通过索引值,找到face(字体文件)里的字形图像,并放到face->glyph字符槽里.
if ( error )
continue;

FT_Get_Glyph(face->glyph, &glyph->image );//然后存储每个文字的字形图像
if ( error )
continue;

 
FT_Glyph_Transform(glyph->image, 0, &glyph->pos );
        //使用FT_Glyph_Transform(),使glyph->image包含位置信息

pen_x += face->glyph->advance.x;     // 以1/64像素点为单位

glyph++;     

}

num_glyphs= glyph- glyphs;               //获取转换成功的文字个数

3)通过glyphs[]存的一行字形图像,计算出边界框

FT_BBox bbox;

bbox.xMin = bbox.yMin = 32000;
bbox.xMax = bbox.yMax = -32000;

       /*判断一行文字的边界框范围*/
       for ( n = 0; n < num_glyphs; n++ )
       {
              FT_BBox glyph_bbox;
              FT_Glyph_Get_CBox(glyphs[n].image, FT_GLYPH_BBOX_TRUNCATE, &glyph_bbox );
                             // FT_GLYPH_BBOX_TRUNCATE:获取的坐标信息以像素坐标为单位

              if (glyph_bbox.xMin < bbox.xMin)
                     bbox.xMin = glyph_bbox.xMin;

              if (glyph_bbox.yMin < bbox.yMin)
                     bbox.yMin = glyph_bbox.yMin;

              if (glyph_bbox.xMax > bbox.xMax)
                     bbox.xMax = glyph_bbox.xMax;

              if (glyph_bbox.yMax > bbox.yMax)
                     bbox.yMax = glyph_bbox.yMax;
       }

4)通过边界框,找到居中显示的坐标信息

       int line_box_width;
       int line_box_height;

       line_box_width  = bbox.xMax - bbox.xMin;              //一行文字的宽度
       line_box_height = bbox.yMax - bbox.yMin;              //一行文字的高度

       pen.x = (var.xres - line_box_width)/2 * 64;          // var.xres:LCD总宽度
       pen.y = (var.yres - line_box_height)/2 * 64;  

5)通过坐标信息,将glyphs[]存的一行字形图像显示出来

for (n = 0; n < num_glyphs; n++)
{                                                                   
     //再次使用FT_Glyph_Transform(),更新glyphs[n].image里的坐标值
       FT_Glyph_Transform(glyphs[n].image, 0, &pen);

  error = FT_Glyph_To_Bitmap(&glyphs[n].image, FT_RENDER_MODE_NORMAL, 0,1);
                    //转化为位图,1:转换后并摧毁glyphs[n].image的内容
  if( !error )
  { 
   FT_BitmapGlyph bit = (FT_BitmapGlyph)glyphs[n].image;  
   draw_bitmap(&glyphs[n].image->bitmap, bit->left, var.yres - bit->top); //打印位图
   FT_Done_Glyph(glyphs[n].image );       //注销一个Glyph
  }
}