一 ： Framebuffer API
1、int open(const char *pathname, int flags)
Example:
int fd_fb;
fd_fb = open("/dev/fb0", O_RDWR);
2、int ioctl(int fd, unsigned long request, ...)
Example:
struct fb_var_screeninfo var;
ioctl(fd_fb, FBIOGET_VSCREENINFO, &var)
According to the request command, the device driver returns the output data
For FBIOGET_VSCREENINFO var return instruction is fb_var_screeninfo structure:
It contains information about LCD: xres (total pixels in x direction), yres (total pixels in y direction), bits_per_pixel (number of bits occupied by each pixel)
According to the information obtained, some variables can be calculated:
Bytes occupied by pixels in each row: line_width = var.xres * var.bits_per_pixel / 8;
Bytes occupied by each pixel: pixel_width = var.bits_per_pixel / 8;
Bytes occupied by all pixels: screen_size = var.xres * var.yres * var.bits_per_pixel / 8;
3、void *mmap(void *addr, size_t length, int prot, int flags,int fd, off_t offset)
Example:
unsigned char *fbmem;
fbmem = (unsigned char *)mmap(NULL , screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);
addr: indicates the starting address of the mapped memory, usually NULL means let the system choose by itself, and return the address after success
length: indicates the size of the content to be mapped
prot: indicates the protection mode of the mapped area
①PROT_EXEC mapping area can be executed
②PROT_READ mapping area can be read and written
③PROT_WRITE mapping area can be written
④PROT_NONE mapping area cannot be accessed
Represents the different characteristics of the mapping area:
①MAP_SHARED means that the data written to the mapping area will be copied back into the file, and the original file will be changed.
②MAP_PRIVATE means that the operation of the mapping area will produce a copy of the mapping file, and any modification of this area will not be written back to the original file content.
Two: FreeType environment construction
1. Download and unzip the installation package
tar xjf freetype-2.4.10.tar.bz2
2. Configuration
--host: compilation tool
--prefix: configure the target directory
jun@zero:~/work/file/application/01_framebuffer/freetype-2.4.10$ ./configure --host=arm-linux-gnueabihf --prefix=/home/jun/work/tool/arm-linux-gcc/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr
3. Compile and install
You need to create a file before compiling and installing: internal
jun@zero:~/work/tool/arm-linux-gcc/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr/include/freetype2/freetype$ mkdir internal -p
Responsible for errors:
'/home/jun/work/tool/arm-linux-gcc/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr/include/freetype2/freetype/internal' Failure: No such file or directory
Compile and install: make install
4. Move the freetype library to avoid the need to specify the path when compiling files later
mv /home/jun/work/tool/arm-linux-gcc/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr/include/freetype2/freetype /home/jun/work/tool/arm-linux-gcc/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr/include/
Three: Introduction to FreeType
1. Header file
#include <ft2build.h>
#include FT_FREETYPE_H
Starting with FreeType 2.1.6, the old header file inclusion scheme is no longer supported. This means that if you do the following, you will now get an error:
#include <freetype / freetype.h>
2. Initialize the library
Create a variable library of type FT_Librart, then pass in the FT_Init_FreeType function, and return 0 successfully
#include <ft2build.h>
#include FT_FREETYPE_H
FT_Library library;
...
error = FT_Init_FreeType( &library );
if ( error )
{
... an error occurred during library initialization ...
}3. Load fonts
Open a font file ".ttf" by calling FT_New_Face, and obtain an FT_Face type object face from it to describe the font.
FT_Face face; /* handle to face object */
error = FT_New_Face( library,
"/usr/share/fonts/truetype/arial.ttf",
0,
&face );
if ( error == FT_Err_Unknown_File_Format )
{
... the font file could be opened and read, but it appears
... that its font format is unsupported
}
else if ( error )
{
... another error code means that the font file could not
... be opened or read, or simply that it is broken...
}If the font file has been loaded into the memory, you can use FT_New_Memory_Face() to get the object face instead of the font file path. Note that you cannot call FT_Done_Face() before releasing the memory.
error = FT_New_Memory_Face( library,
buffer, /* first byte in memory */
size, /* size in bytes */
0, /* face_index */
&face );4. Visit face
You can directly access face data by reference
FT_GlyphSlot slot;
slot = face->glyph;5. Set the pixel size
a. For a 300x300dpi device, the character size is set to 16pt
error = FT_Set_Char_Size(
face, /* handle to face object */
0, /* char_width in 1/64th of points */
16*64, /* char_height in 1/64th of points */
300, /* horizontal device resolution */
300 ); /* vertical device resolution */b. Specify the pixel size by yourself, the value of one dimension is 0 means the same as the other dimension
error = FT_Set_Pixel_Sizes(
face, /* handle to face object */
0, /* pixel_width */
16 ); /* pixel_height */6. Glyph conversion
When loading a glyph image, you can perform a specified transformation, which is only applicable to the vector font format
FT_Vector pen;
FT_Matrix matrix; /* transformation matrix */
error = FT_Set_Transform(
face, /* target face object */
&matrix, /* pointer to 2x2 matrix */
&pen); /* pointer to 2d vector */7, font loading
wchar_t *chinese_str = L"繁";
error = FT_Load_Char( face, chinese_str[0], FT_LOAD_RENDER );Four: Comprehensive example
#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 <sys/ioctl.h>
#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_GLYPH_H
#define FONTDATAMAX 4096
static const unsigned char fontdata_8x16[FONTDATAMAX] = {
... ...
/* 1 0x01 '^A' */
0x00, /* 00000000 */
0x00, /* 00000000 */
0x7e, /* 01111110 */
0x81, /* 10000001 */
0xa5, /* 10100101 */
0x81, /* 10000001 */
0x81, /* 10000001 */
0xbd, /* 10111101 */
0x99, /* 10011001 */
0x81, /* 10000001 */
0x81, /* 10000001 */
0x7e, /* 01111110 */
0x00, /* 00000000 */
0x00, /* 00000000 */
0x00, /* 00000000 */
0x00, /* 00000000 */
... ...
}
int fd_fb;
struct fb_var_screeninfo var; /* Current var */
int screen_size;
unsigned char *fbmem;
unsigned int line_width;
unsigned int pixel_width;
int fd_hzk16;
struct stat hzk_stat;
unsigned char *hzkmem;
/**********************************************************************
* 函数名称： lcd_put_pixel
* 功能描述： 在LCD指定位置上输出指定颜色（描点）
* 输入参数： x坐标，y坐标，颜色
* 输出参数： 无
***********************************************************************/
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;
}
}
}
/**********************************************************************
* 函数名称： lcd_put_ascii
* 功能描述： 在LCD指定位置上显示一个8*16的字符
* 输入参数： x坐标，y坐标，ascii码
***********************************************************************/
void lcd_put_ascii(int x, int y, unsigned char c)
{
unsigned char *dots = (unsigned char *)&fontdata_8x16[c*16];
int i, b;
unsigned char byte;
for (i = 0; i < 16; i++)
{
byte = dots[i];
for (b = 7; b >= 0; b--)
{
if (byte & (1<<b))
{
/* show */
lcd_put_pixel(x+7-b, y+i, 0xffffff); /* 白 */
}
else
{
/* hide */
lcd_put_pixel(x+7-b, y+i, 0); /* 黑 */
}
}
}
}
/**********************************************************************
* 函数名称： lcd_put_chinese
* 功能描述： 在LCD指定位置上显示一个16*16的汉字
* 输入参数： x坐标，y坐标，ascii码
***********************************************************************/
void lcd_put_chinese(int x, int y, unsigned char *str)
{
unsigned int area = str[0] - 0xA1;
unsigned int where = str[1] - 0xA1;
unsigned char *dots = hzkmem + (area * 94 + where)*32;
unsigned char byte;
int i, j, b;
for (i = 0; i < 16; i++)
for (j = 0; j < 2; j++)
{
byte = dots[i*2 + j];
for (b = 7; b >=0; b--)
{
if (byte & (1<<b))
{
/* show */
lcd_put_pixel(x+j*8+7-b, y+i, 0xffffff); /* 白 */
}
else
{
/* hide */
lcd_put_pixel(x+j*8+7-b, y+i, 0); /* 黑 */
}
}
}
}
/**********************************************************************
* 函数名称： draw_bitmap
* 功能描述： 根据bitmap位图，在LCD指定位置显示汉字
* 输入参数： x坐标，y坐标，位图指针
***********************************************************************/
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)
{
unsigned char str[] = "中";
wchar_t *chinese_str = L"繁";
FT_Library library;
FT_Face face;
int error;
FT_Vector pen;
FT_GlyphSlot slot;
FT_Matrix matrix; /* transformation matrix */
double angle;
if (argc != 3)
{
printf("Usage : %s <font_file> <angle>\n", argv[0]);
return -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;
}
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;
}
fd_hzk16 = open("HZK16", O_RDONLY);
if (fd_hzk16 < 0)
{
printf("can't open HZK16\n");
return -1;
}
if(fstat(fd_hzk16, &hzk_stat))
{
printf("can't get fstat\n");
return -1;
}
hzkmem = (unsigned char *)mmap(NULL , hzk_stat.st_size, PROT_READ, MAP_SHARED, fd_hzk16, 0);
if (hzkmem == (unsigned char *)-1)
{
printf("can't mmap for hzk16\n");
return -1;
}
/* 清屏: 全部设为黑色 */
memset(fbmem, 0, screen_size);
lcd_put_ascii(var.xres/2, var.yres/2, 'A');
printf("chinese code: %02x %02x\n", str[0], str[1]);
lcd_put_chinese(var.xres/2 + 8, var.yres/2, str);
/* 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 = var.xres/2 + 8 + 16
* lcd_y = var.yres/2 + 16
* 笛卡尔座标系:
* x = lcd_x = var.xres/2 + 8 + 16
* y = var.yres - lcd_y = var.yres/2 - 16
*/
pen.x = (var.xres/2 + 8 + 16) * 64;
pen.y = (var.yres/2 - 16) * 64;
angle = ( 1.0 * strtoul(argv[2], NULL, 0) / 360 ) * 3.14159 * 2; /* use 25 degrees */
/* 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 );
/* set transformation */
FT_Set_Transform( face, &matrix, &pen);
/* load glyph image into the slot (erase previous one) */
error = FT_Load_Char( face, chinese_str[0], 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);
return 0;
}