LittleVGL 源码分析--src/lv_misc/lv_math.h

/**
 * @file math_base.h
 *
 */

#ifndef LV_MATH_H
#define LV_MATH_H

#ifdef __cplusplus
extern "C" {
#endif

/*********************
 *      INCLUDES
 *********************/
#include 

/*********************
 *      DEFINES
 *********************/
#define LV_MATH_MIN(a, b) ((a) < (b) ? (a) : (b))
#define LV_MATH_MAX(a, b) ((a) > (b) ? (a) : (b))
#define LV_MATH_ABS(x) ((x) > 0 ? (x) : (-(x)))

#define LV_TRIGO_SIN_MAX 32767
#define LV_TRIGO_SHIFT 15 /**<  >> LV_TRIGO_SHIFT to normalize*/  //规范化

#define LV_BEZIER_VAL_MAX 1024 /**< Max time in Bezier functions (not [0..1] to use integers) */ //贝塞尔函数中的最长时间（不是[0..1]使用整数）
#define LV_BEZIER_VAL_SHIFT 10 /**< log2(LV_BEZIER_VAL_MAX): used to normalize up scaled values*/ //log2（LV_BEZIER_VAL_MAX）：用于标准化按比例放大的值

/**********************
 *      TYPEDEFS
 **********************/

/**********************
 * GLOBAL PROTOTYPES
 **********************/

/**
 * Return with sinus of an angle    
 * @param angle  角度
 * @return sinus of 'angle'. sin(-90) = -32767, sin(90) = 32767  
 */
int16_t lv_trigo_sin(int16_t angle);

/**
 * Calculate a value of a Cubic Bezier function.计算一个三次贝塞尔函数的值。
 * @param t time in range of [0..LV_BEZIER_VAL_MAX]  时间范围
 * @param u0 start values in range of [0..LV_BEZIER_VAL_MAX]起始值范围
 * @param u1 control value 1 values in range of [0..LV_BEZIER_VAL_MAX]控制值1范围
 * @param u2 control value 2 in range of [0..LV_BEZIER_VAL_MAX]控制值2范围
 * @param u3 end values in range of [0..LV_BEZIER_VAL_MAX]结束值范围
 * @return the value calculated from the given parameters in range of [0..LV_BEZIER_VAL_MAX] 根据给定参数范围
 */
int32_t lv_bezier3(uint32_t t, int32_t u0, int32_t u1, int32_t u2, int32_t u3);

/**********************
 *      MACROS
 **********************/

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif

/**
 * @file lv_math.c
 *
 */

/*********************
 *      INCLUDES
 *********************/
#include "lv_math.h"
#include 
#include 

/*********************
 *      DEFINES
 *********************/

/**********************
 *      TYPEDEFS
 **********************/

/**********************
 *  STATIC PROTOTYPES
 **********************/

/**********************
 *  STATIC VARIABLES
 **********************/
static int16_t sin0_90_table[] = {
    0,     572,   1144,  1715,  2286,  2856,  3425,  3993,  4560,  5126,  5690,  6252,  6813,  7371,  7927,  8481,
    9032,  9580,  10126, 10668, 11207, 11743, 12275, 12803, 13328, 13848, 14364, 14876, 15383, 15886, 16383, 16876,
    17364, 17846, 18323, 18794, 19260, 19720, 20173, 20621, 21062, 21497, 21925, 22347, 22762, 23170, 23571, 23964,
    24351, 24730, 25101, 25465, 25821, 26169, 26509, 26841, 27165, 27481, 27788, 28087, 28377, 28659, 28932, 29196,
    29451, 29697, 29934, 30162, 30381, 30591, 30791, 30982, 31163, 31335, 31498, 31650, 31794, 31927, 32051, 32165,
    32269, 32364, 32448, 32523, 32587, 32642, 32687, 32722, 32747, 32762, 32767};

/**********************
 *      MACROS
 **********************/

/**********************
 *   GLOBAL FUNCTIONS
 **********************/

/**
 * Return with sinus of an angle
 * @param angle
 * @return sinus of 'angle'. sin(-90) = -32767, sin(90) = 32767
 */
int16_t lv_trigo_sin(int16_t angle)
{
    int16_t ret = 0;
    angle       = angle % 360;

    if(angle < 0) angle = 360 + angle;

    if(angle < 90) {
        ret = sin0_90_table[angle];
    } else if(angle >= 90 && angle < 180) {
        angle = 180 - angle;
        ret   = sin0_90_table[angle];
    } else if(angle >= 180 && angle < 270) {
        angle = angle - 180;
        ret   = -sin0_90_table[angle];
    } else { /*angle >=270*/
        angle = 360 - angle;
        ret   = -sin0_90_table[angle];
    }

    return ret;
}

/**
 * Calculate a value of a Cubic Bezier function.
 * @param t time in range of [0..LV_BEZIER_VAL_MAX]
 * @param u0 start values in range of [0..LV_BEZIER_VAL_MAX]
 * @param u1 control value 1 values in range of [0..LV_BEZIER_VAL_MAX]
 * @param u2 control value 2 in range of [0..LV_BEZIER_VAL_MAX]
 * @param u3 end values in range of [0..LV_BEZIER_VAL_MAX]
 * @return the value calculated from the given parameters in range of [0..LV_BEZIER_VAL_MAX]
 */
int32_t lv_bezier3(uint32_t t, int32_t u0, int32_t u1, int32_t u2, int32_t u3)
{
    uint32_t t_rem  = 1024 - t;
    uint32_t t_rem2 = (t_rem * t_rem) >> 10;
    uint32_t t_rem3 = (t_rem2 * t_rem) >> 10;
    uint32_t t2     = (t * t) >> 10;
    uint32_t t3     = (t2 * t) >> 10;

    uint32_t v1 = ((uint32_t)t_rem3 * u0) >> 10;
    uint32_t v2 = ((uint32_t)3 * t_rem2 * t * u1) >> 20;
    uint32_t v3 = ((uint32_t)3 * t_rem * t2 * u2) >> 20;
    uint32_t v4 = ((uint32_t)t3 * u3) >> 10;

    return v1 + v2 + v3 + v4;
}

/**********************
 *   STATIC FUNCTIONS
 **********************/

总结：一个sin角度函数 还没搞懂

   三次贝塞尔函数，还没搞懂：https://blog.csdn.net/qq_39328456/article/details/100895685