FreeType矢量字体对颜色的显示（妙用）

在网上发现FreeType矢量字体对颜色的显示这类文章较少，这里就给出一个示例代码：

show_lines.c

#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 <stdlib.h>

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

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;
int number;

unsigned int color_array[6]={
					0x0000FF , /* blue */
					0x00FF00 , /* green */
					0x00FFFF ,/* blackish green  */
					0xFF0000 ,/* red */
					0xFF00FF ,/* carmine */
					0xFFFF00 ,/* yellow */
					};

/* 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);
			if(color!=0)  /* 这里非常重要，有些轮廓信息是0，就是字体空白区域*/
			{
			red   = (color_array[number] >> 16) & 0xff;
			green = (color_array[number] >> 8) & 0xff;
			blue  = (color_array[number] >> 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)
{
	wchar_t *wstr1 = L"网络人VS灰鸽子";

	FT_Library	  library;
	FT_Face 	  face;
	int error;
    FT_Vector     pen;
	FT_GlyphSlot  slot;
	int i;
	int font_size;

	if (argc != 4)
	{
		printf("Usage : %s <font_file> <font_size> <color number0~5>\n", argv[0]);
		return -1;
	}
	font_size=atol(argv[2]);	
	number   =atol(argv[3]);
	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;
	}

	/* 清屏: 全部设为黑色 */
	memset(fbmem, 0, screen_size);

	/* 显示矢量字体 */
	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 */	
	slot = face->glyph;

	FT_Set_Pixel_Sizes(face,24, 0);

	/* 确定座标:
	 * lcd_x = 0
	 * lcd_y = font_size
	 * 笛卡尔座标系:
	 * x = lcd_x = 0
	 * y = var.yres - lcd_y = var.yres - 24
	 */
	pen.x = 0 * 64;
	pen.y = (var.yres - 24) * 64;

	for (i = 0; i < wcslen(wstr1); i++)
	{
	    /* set transformation */
	    FT_Set_Transform( face, 0, &pen);

	    /* load glyph image into the slot (erase previous one) */
	    error = FT_Load_Char( face, wstr1[i], FT_LOAD_RENDER );
		if (error)
		{
			printf("FT_Load_Char error\n");
			return -1;
		}
		
	    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;

	}
	return 0;	
}

编译：arm-linux-gcc show_lines.c -o show_lines -finput-charset=GBK -fexec-charset=UTF-8 -lfreetype

中文显示需要添加编码的支持。不然编译器通不过，编译器默认输入编码是UTF-8