freetype-example1.c

/* example1.c */

15年8月21日20:12:42

/* 代码如下*/

/* This small program shows how to print a rotated string with the */

/* FreeType 2 library. */

#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 80

#define HEIGHT 80

/* origin is the upper left corner */

unsigned char image[HEIGHT][WIDTH];

/* 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;

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 >= WIDTH || j >= HEIGHT )

continue;

image[j][i] |= bitmap->buffer[q * bitmap->width + p];

}

}

}

void

show_image( void )

{

int i, j;

for ( i = 0; i < HEIGHT; i++ )

{

printf("%02d", i);

for ( j = 0; j < WIDTH; j++ )

putchar( image[i][j] == 0 ? ' '

: image[i][j] < 128 ? '+'

: '*' );

putchar( '\n' );

}

}

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 target_height;

int n, num_chars;

//int chinese_str[] = {0x97e6, 0x4e1c, 0x5c71, 0x0067};

wchar_t *chinese_str = L"闫gif";

unsigned int *p = (wchar_t *)chinese_str;

int i;

FT_BBox bbox;

FT_Glyph glyph;

printf("Unicode : \n");

for (i = 0; i < wcslen(chinese_str); i++)

{

printf(" 0x%x", p[i]);

}

printf("\n");

//return 0;

if ( argc != 3 )

{

fprintf ( stderr, "usage: %s font sample-text\n", argv[0] );

exit( 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 */

/* error handling omitted */

#else

FT_Set_Pixel_Sizes(face, 24, 0);

#endif

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 );

/* the pen position in 26.6 cartesian space coordinates; */

/* start at (0,40) relative to the upper left corner */

pen.x = 0 * 64;

pen.y = ( target_height - 40 ) * 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);

/* now, draw to our target surface (convert position) */

draw_bitmap( &slot->bitmap,

slot->bitmap_left,

target_height - slot->bitmap_top );

printf("Unicode : 0x%x\n", chinese_str[n]);

printf("originx = %d, originy = %d\n", pen.x/64, pen.y/64);

printf("xMin = %d, xMax = %d, yMin = %d, yMax = %d\n", bbox.xMin, bbox.xMax, bbox.yMin, bbox.yMax);

printf("slot->advance.x/64 = %d, slot->advance.y/64 = %d\n", slot- >advance.x/64, slot->advance.y/64);

/* increment pen position */

pen.x += slot->advance.x;

pen.y += slot->advance.y;

}

show_image();

FT_Done_Face ( face );

FT_Done_FreeType( library );

return 0;

}

/* EOF */

想象一个文字的显示过程：

（1）给定一个文字，‘A’：0x41， “中”：GBK， unicode；可以确定它的编码值；

（2）根据“编码值”，从字体文件中找到对应的“glyph”；

（3）设置字体大小；

（4）用某些函数把glyph里的点缩放为所需的字体大小；

（5）转换为位图点阵；

（6）在LCD上面显示出来。

怎么写代码？

（1）初始化：FT_Init_FreeType（）

（2）加载字体face：FT_New_Face（）

（3）设置字体大小：FT_Set_Char_Size（）

FT_Set_Pixel_Sizes（）

（4）根据编码值加载glyph：

1）找到编码值：glyph_index = FT_Get_Char_Index()；

2）取出：FT_Load_Glyph();

转换为位图：FT_Render_Glyph（）；

其中第（4）步，可以简单地用一个函数代替：FT_Load_Char(face, charcode, FT_LOAD_RENDER);

（5）变换，如移动/旋转等：FT_Set_Transform()。

写代码这几步，详细的可以参考《freetype使用帮助.pdf》，上面将的很详细。上面的代码在它的一个例子基础上进行修改，让这个例子可以运行在PC电脑上面。