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 \n",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->width: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\n");
return ;
}
error = FT_New_Face( library, argv, 0, &face ); /* create face object */
if(error)
{
printf("FT_New_Face ERROR\n");
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\n");
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 \n", argv[0] );
return 0;
}
fd_fb=open("/dev/fb0", O_RDWR);
if(fd_fb<0)
{
printf("can't open /dev/fb0 \n");
return 0;
}
if(ioctl(fd_fb,FBIOGET_VSCREENINFO,&fb_var)<0)
{
printf("can't get var \n");
return 0;
}
if(ioctl(fd_fb,FBIOGET_FSCREENINFO,&fb_fix)<0)
{
printf("can't get fix \n");
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 \n");
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
}
}