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图片文档倾斜矫正算法附完整c代码

原作者: [db:作者] 来自: [db:来源] 收藏 邀请

 2年前在学习图像算法的时候看到一个文档倾斜矫正的算法。

也就是说能将一些文档图像进行旋转矫正，

当然这个算法一般用于一些文档扫描软件做后处理

或者用于ocr 文字识别做前处理。

相关的关键词: 抗倾斜 反倾斜  Deskew 等等。

最简单算法实现思路，采用 霍夫变换(Hough Transform)进行直线检测，

当然也可以用霍夫变换检测圆。

在倾斜矫正算法中，自然就是检测直线。

通过对检测出来的直线进行角度判断，

一般取 认可度最高的几条直线进行计算，

最后求取均衡后的角度值。

进行图像角度的旋转即可。

 

大概算法步骤如下：

1.转换为灰度图

2.判断是否为文本图片，如果不是进行 进行 反相操作

3.检测直线，进行角度判断

4.通过角度进行图像旋转

 

这么一个基本思路，当然想要检测得更加精准，

可以做一些文本区域判断，图像修复增强之类的前处理操作。

最近有点强迫症犯了，开始回归本源，强迫自己用c语言来实现，

fastsin以及fastcos 来自 arm公司的开源项目。

霍夫变换相关算法原理，请移步 百度 google 维基百科。

或直接看代码实现，可了悟于心。

有事没事，多看看业内大公司的开源项目，

萝卜白菜都有，重点是学习其思路。

嗯，有些网友可能会说，opencv一两行代码就可以做到了。

对的，一些sdk,api,开源框架一两句代码是做到了，

知道，用到，与真正做到，这是两条路。

我只想说一句，愿世界和平。

附完整代码:

//如果是Windows的话，调用系统API ShellExecuteA打开图片
#if defined(_MSC_VER)
#define _CRT_SECURE_NO_WARNINGS
#include <windows.h>
#define USE_SHELL_OPEN
#endif

#define STB_IMAGE_STATIC
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
//ref:https://github.com/nothings/stb/blob/master/stb_image.h
#define TJE_IMPLEMENTATION
#include "tiny_jpeg.h" 
//ref:https://github.com/serge-rgb/TinyJPEG/blob/master/tiny_jpeg.h
#include <math.h>
#include <io.h>    
#include <math.h>
#include <stdlib.h>
#include <stdbool.h>

//计时 
#include <stdint.h>
#if   defined(__APPLE__)
# include <mach/mach_time.h>
#elif defined(_WIN32)
# define WIN32_LEAN_AND_MEAN
# include <windows.h>
#else // __linux
# include <time.h>
# ifndef  CLOCK_MONOTONIC //_RAW
#  define CLOCK_MONOTONIC CLOCK_REALTIME
# endif
#endif
static
uint64_t nanotimer() {
    static int ever = 0;
#if defined(__APPLE__)
    static mach_timebase_info_data_t frequency;
    if (!ever) {
        if (mach_timebase_info(&frequency) != KERN_SUCCESS) {
            return 0;
        }
        ever = 1;
    }
    return;
#elif defined(_WIN32)
    static LARGE_INTEGER frequency;
    if (!ever) {
        QueryPerformanceFrequency(&frequency);
        ever = 1;
    }
    LARGE_INTEGER t;
    QueryPerformanceCounter(&t);
    return (t.QuadPart * (uint64_t)1e9) / frequency.QuadPart;
#else // __linux
    struct timespec t;
    if (!ever) {
        if (clock_gettime(CLOCK_MONOTONIC, &spec) != 0) {
            return 0;
        }
        ever = 1;
    }
    clock_gettime(CLOCK_MONOTONIC, &spec);
    return (t.tv_sec * (uint64_t)1e9) + t.tv_nsec;
#endif
}


static double now()
{
    static uint64_t epoch = 0;
    if (!epoch) {
        epoch = nanotimer();
    }
    return (nanotimer() - epoch) / 1e9;
};

double  calcElapsed(double start, double end)
{
    double took = -start;
    return took + end;
}



//存储当前传入文件位置的变量
char  saveFile[1024];
//加载图片
unsigned char * loadImage(const char *filename, int *Width, int *Height, int *Channels)
{
    return   stbi_load(filename, Width, Height, Channels, 0);
}
//保存图片
void saveImage(const char *filename, int Width, int Height, int Channels, unsigned char *Output)
{

    memcpy(saveFile + strlen(saveFile), filename, strlen(filename));
    *(saveFile + strlen(saveFile) + 1) = 0;
    //保存为jpg
    if (!tje_encode_to_file(saveFile, Width, Height, Channels, true, Output))
    {
        fprintf(stderr, "写入 JPEG 文件失败.\n");
        return;
    }

#ifdef USE_SHELL_OPEN 
    ShellExecuteA(NULL, "open", saveFile, NULL, NULL, SW_SHOW);
#else
    //其他平台暂不实现
#endif
}


#ifndef ClampToByte
#define  ClampToByte(  v )  ( ((unsigned)(int)(v)) <(255) ? (v) : ((int)(v) < 0) ? (0) : (255)) 
#endif 

#define M_PI 3.14159265358979323846f

typedef struct cpu_HoughLine
{
    float Theta;
    int Radius;
    int Intensity;
    float RelativeIntensity;
} cpu_HoughLine;


typedef struct cpu_rect
{
    int  x;
    int  y;
    int  Width;
    int  Height;
} cpu_rect;

#ifndef clamp
#define clamp(value,min,max)  ((value) > (max )? (max ): (value) < (min) ? (min) : (value))
#endif 

#define FAST_MATH_TABLE_SIZE  512

const float sinTable_f32[FAST_MATH_TABLE_SIZE + 1] = {
    0.00000000f, 0.01227154f, 0.02454123f, 0.03680722f, 0.04906767f, 0.06132074f,
    0.07356456f, 0.08579731f, 0.09801714f, 0.11022221f, 0.12241068f, 0.13458071f,
    0.14673047f, 0.15885814f, 0.17096189f, 0.18303989f, 0.19509032f, 0.20711138f,
    0.21910124f, 0.23105811f, 0.24298018f, 0.25486566f, 0.26671276f, 0.27851969f,
    0.29028468f, 0.30200595f, 0.31368174f, 0.32531029f, 0.33688985f, 0.34841868f,
    0.35989504f, 0.37131719f, 0.38268343f, 0.39399204f, 0.40524131f, 0.41642956f,
    0.42755509f, 0.43861624f, 0.44961133f, 0.46053871f, 0.47139674f, 0.48218377f,
    0.49289819f, 0.50353838f, 0.51410274f, 0.52458968f, 0.53499762f, 0.54532499f,
    0.55557023f, 0.56573181f, 0.57580819f, 0.58579786f, 0.59569930f, 0.60551104f,
    0.61523159f, 0.62485949f, 0.63439328f, 0.64383154f, 0.65317284f, 0.66241578f,
    0.67155895f, 0.68060100f, 0.68954054f, 0.69837625f, 0.70710678f, 0.71573083f,
    0.72424708f, 0.73265427f, 0.74095113f, 0.74913639f, 0.75720885f, 0.76516727f,
    0.77301045f, 0.78073723f, 0.78834643f, 0.79583690f, 0.80320753f, 0.81045720f,
    0.81758481f, 0.82458930f, 0.83146961f, 0.83822471f, 0.84485357f, 0.85135519f,
    0.85772861f, 0.86397286f, 0.87008699f, 0.87607009f, 0.88192126f, 0.88763962f,
    0.89322430f, 0.89867447f, 0.90398929f, 0.90916798f, 0.91420976f, 0.91911385f,
    0.92387953f, 0.92850608f, 0.93299280f, 0.93733901f, 0.94154407f, 0.94560733f,
    0.94952818f, 0.95330604f, 0.95694034f, 0.96043052f, 0.96377607f, 0.96697647f,
    0.97003125f, 0.97293995f, 0.97570213f, 0.97831737f, 0.98078528f, 0.98310549f,
    0.98527764f, 0.98730142f, 0.98917651f, 0.99090264f, 0.99247953f, 0.99390697f,
    0.99518473f, 0.99631261f, 0.99729046f, 0.99811811f, 0.99879546f, 0.99932238f,
    0.99969882f, 0.99992470f, 1.00000000f, 0.99992470f, 0.99969882f, 0.99932238f,
    0.99879546f, 0.99811811f, 0.99729046f, 0.99631261f, 0.99518473f, 0.99390697f,
    0.99247953f, 0.99090264f, 0.98917651f, 0.98730142f, 0.98527764f, 0.98310549f,
    0.98078528f, 0.97831737f, 0.97570213f, 0.97293995f, 0.97003125f, 0.96697647f,
    0.96377607f, 0.96043052f, 0.95694034f, 0.95330604f, 0.94952818f, 0.94560733f,
    0.94154407f, 0.93733901f, 0.93299280f, 0.92850608f, 0.92387953f, 0.91911385f,
    0.91420976f, 0.90916798f, 0.90398929f, 0.89867447f, 0.89322430f, 0.88763962f,
    0.88192126f, 0.87607009f, 0.87008699f, 0.86397286f, 0.85772861f, 0.85135519f,
    0.84485357f, 0.83822471f, 0.83146961f, 0.82458930f, 0.81758481f, 0.81045720f,
    0.80320753f, 0.79583690f, 0.78834643f, 0.78073723f, 0.77301045f, 0.76516727f,
    0.75720885f, 0.74913639f, 0.74095113f, 0.73265427f, 0.72424708f, 0.71573083f,
    0.70710678f, 0.69837625f, 0.68954054f, 0.68060100f, 0.67155895f, 0.66241578f,
    0.65317284f, 0.64383154f, 0.63439328f, 0.62485949f, 0.61523159f, 0.60551104f,
    0.59569930f, 0.58579786f, 0.57580819f, 0.56573181f, 0.55557023f, 0.54532499f,
    0.53499762f, 0.52458968f, 0.51410274f, 0.50353838f, 0.49289819f, 0.48218377f,
    0.47139674f, 0.46053871f, 0.44961133f, 0.43861624f, 0.42755509f, 0.41642956f,
    0.40524131f, 0.39399204f, 0.38268343f, 0.37131719f, 0.35989504f, 0.34841868f,
    0.33688985f, 0.32531029f, 0.31368174f, 0.30200595f, 0.29028468f, 0.27851969f,
    0.26671276f, 0.25486566f, 0.24298018f, 0.23105811f, 0.21910124f, 0.20711138f,
    0.19509032f, 0.18303989f, 0.17096189f, 0.15885814f, 0.14673047f, 0.13458071f,
    0.12241068f, 0.11022221f, 0.09801714f, 0.08579731f, 0.07356456f, 0.06132074f,
    0.04906767f, 0.03680722f, 0.02454123f, 0.01227154f, 0.00000000f, -0.01227154f,
    -0.02454123f, -0.03680722f, -0.04906767f, -0.06132074f, -0.07356456f,
    -0.08579731f, -0.09801714f, -0.11022221f, -0.12241068f, -0.13458071f,
    -0.14673047f, -0.15885814f, -0.17096189f, -0.18303989f, -0.19509032f,
    -0.20711138f, -0.21910124f, -0.23105811f, -0.24298018f, -0.25486566f,
    -0.26671276f, -0.27851969f, -0.29028468f, -0.30200595f, -0.31368174f,
    -0.32531029f, -0.33688985f, -0.34841868f, -0.35989504f, -0.37131719f,
    -0.38268343f, -0.39399204f, -0.40524131f, -0.41642956f, -0.42755509f,
    -0.43861624f, -0.44961133f, -0.46053871f, -0.47139674f, -0.48218377f,
    -0.49289819f, -0.50353838f, -0.51410274f, -0.52458968f, -0.53499762f,
    -0.54532499f, -0.55557023f, -0.56573181f, -0.57580819f, -0.58579786f,
    -0.59569930f, -0.60551104f, -0.61523159f, -0.62485949f, -0.63439328f,
    -0.64383154f, -0.65317284f, -0.66241578f, -0.67155895f, -0.68060100f,
    -0.68954054f, -0.69837625f, -0.70710678f, -0.71573083f, -0.72424708f,
    -0.73265427f, -0.74095113f, -0.74913639f, -0.75720885f, -0.76516727f,
    -0.77301045f, -0.78073723f, -0.78834643f, -0.79583690f, -0.80320753f,
    -0.81045720f, -0.81758481f, -0.82458930f, -0.83146961f, -0.83822471f,
    -0.84485357f, -0.85135519f, -0.85772861f, -0.86397286f, -0.87008699f,
    -0.87607009f, -0.88192126f, -0.88763962f, -0.89322430f, -0.89867447f,
    -0.90398929f, -0.90916798f, -0.91420976f, -0.91911385f, -0.92387953f,
    -0.92850608f, -0.93299280f, -0.93733901f, -0.94154407f, -0.94560733f,
    -0.94952818f, -0.95330604f, -0.95694034f, -0.96043052f, -0.96377607f,
    -0.96697647f, -0.97003125f, -0.97293995f, -0.97570213f, -0.97831737f,
    -0.98078528f, -0.98310549f, -0.98527764f, -0.98730142f, -0.98917651f,
    -0.99090264f, -0.99247953f, -0.99390697f, -0.99518473f, -0.99631261f,
    -0.99729046f, -0.99811811f, -0.99879546f, -0.99932238f, -0.99969882f,
    -0.99992470f, -1.00000000f, -0.99992470f, -0.99969882f, -0.99932238f,
    -0.99879546f, -0.99811811f, -0.99729046f, -0.99631261f, -0.99518473f,
    -0.99390697f, -0.99247953f, -0.99090264f, -0.98917651f, -0.98730142f,
    -0.98527764f, -0.98310549f, -0.98078528f, -0.97831737f, -0.97570213f,
    -0.97293995f, -0.97003125f, -0.96697647f, -0.96377607f, -0.96043052f,
    -0.95694034f, -0.95330604f, -0.94952818f, -0.94560733f, -0.94154407f,
    -0.93733901f, -0.93299280f, -0.92850608f, -0.92387953f, -0.91911385f,
    -0.91420976f, -0.90916798f, -0.90398929f, -0.89867447f, -0.89322430f,
    -0.88763962f, -0.88192126f, -0.87607009f, -0.87008699f, -0.86397286f,
    -0.85772861f, -0.85135519f, -0.84485357f, -0.83822471f, -0.83146961f,
    -0.82458930f, -0.81758481f, -0.81045720f, -0.80320753f, -0.79583690f,
    -0.78834643f, -0.78073723f, -0.77301045f, -0.76516727f, -0.75720885f,
    -0.74913639f, -0.74095113f, -0.73265427f, -0.72424708f, -0.71573083f,
    -0.70710678f, -0.69837625f, -0.68954054f, -0.68060100f, -0.67155895f,
    -0.66241578f, -0.65317284f, -0.64383154f, -0.63439328f, -0.62485949f,
    -0.61523159f, -0.60551104f, -0.59569930f, -0.58579786f, -0.57580819f,
    -0.56573181f, -0.55557023f, -0.54532499f, -0.53499762f, -0.52458968f,
    -0.51410274f, -0.50353838f, -0.49289819f, -0.48218377f, -0.47139674f,
    -0.46053871f, -0.44961133f, -0.43861624f, -0.42755509f, -0.41642956f,
    -0.40524131f, -0.39399204f, -0.38268343f, -0.37131719f, -0.35989504f,
    -0.34841868f, -0.33688985f, -0.32531029f, -0.31368174f, -0.30200595f,
    -0.29028468f, -0.27851969f, -0.26671276f, -0.25486566f, -0.24298018f,
    -0.23105811f, -0.21910124f, -0.20711138f, -0.19509032f, -0.18303989f,
    -0.17096189f, -0.15885814f, -0.14673047f, -0.13458071f, -0.12241068f,
    -0.11022221f, -0.09801714f, -0.08579731f, -0.07356456f, -0.06132074f,
    -0.04906767f, -0.03680722f, -0.02454123f, -0.01227154f, -0.00000000f
};

inline float  fastSin(
    float x)
{
    float sinVal, fract, in;
    unsigned short  index;
    float a, b;
    int n;
    float findex;

    in = x * 0.159154943092f;

    n = (int)in;

    if (x < 0.0f)
    {
        n--;
    }

    in = in - (float)n;

    findex = (float)FAST_MATH_TABLE_SIZE * in;
    if (findex >= 512.0f) {
        findex -= 512.0f;
    }

    index = ((unsigned short)findex) & 0x1ff;

    fract = findex - (float)index;

    a = sinTable_f32[index];
    b = sinTable_f32[index + 1];

    sinVal = (1.0f - fract)*a + fract*b;

    return (sinVal);
}

inline float  fastCos(
    float x)
{
    float cosVal, fract, in;
    unsigned short index;
    float a, b;
    int n;
    float findex;

    in = x * 0.159154943092f + 0.25f;

    n = (int)in;

    if (in < 0.0f)
    {
        n--;
    }

    in = in - (float)n;

    findex = (float)FAST_MATH_TABLE_SIZE * in;
    index = ((unsigned short)findex) & 0x1ff;

    fract = findex - (float)index;

    a = sinTable_f32[index];
    b = sinTable_f32[index + 1];

    cosVal = (1.0f - fract)*a + fract*b;

    return (cosVal);
}

void CPUImageGrayscaleFilter(unsigned char* Input, unsigned char* Output, int  Width, int  Height, int Stride)
{
    int Channels = Stride / Width;

    const int B_WT = (int)(0.114 * 256 + 0.5);
    const int G_WT = (int)(0.587 * 256 + 0.5);
    const int R_WT = 256 - B_WT - G_WT;            //     int(0.299 * 256 + 0.5);
    int Channel = Stride / Width;
    if (Channel == 3)
    {
        for (int Y = 0; Y < Height; Y++)
        {
            unsigned char *LinePS = Input + Y * Stride;
            unsigned char *LinePD = Output + Y * Width;
            int X = 0;
            for (; X < Width - 4; X += 4, LinePS += Channel * 4)
            {
                LinePD[X + 0] = (B_WT * LinePS[0] + G_WT * LinePS[1] + R_WT * LinePS[2]) >> 8;
                LinePD[X + 1] = (B_WT * LinePS[3] + G_WT * LinePS[4] + R_WT * LinePS[5]) >> 8;
                LinePD[X + 2] = (B_WT * LinePS[6] + G_WT * LinePS[7] + R_WT * LinePS[8]) >> 8;
                LinePD[X + 3] = (B_WT * LinePS[9] + G_WT * LinePS[10] + R_WT * LinePS[11]) >> 8;
            }
            for (; X < Width; X++, LinePS += Channel)
            {
                LinePD[X] = (B_WT * LinePS[0] + G_WT * LinePS[1] + R_WT * LinePS[2]) >> 8;
            }
        }
    }
    else if (Channel == 4)
    {
        for (int Y = 0; Y < Height; Y++)
        {
            unsigned char *LinePS = Input + Y * Stride;
            unsigned char *LinePD = Output + Y * Width;
            int X = 0;
            for (; X < Width - 4; X += 4, LinePS += Channel * 4)
            {
                LinePD[X + 0] = (B_WT * LinePS[0] + G_WT * LinePS[1] + R_WT * LinePS[2]) >> 8;
                LinePD[X + 1] = (B_WT * LinePS[4] + G_WT * LinePS[5] + R_WT * LinePS[6]) >> 8;
                LinePD[X + 2] = (B_WT * LinePS[8] + G_WT * LinePS[9] + R_WT * LinePS[10]) >> 8;
                LinePD[X + 3] = (B_WT * LinePS[12] + G_WT * LinePS[13] + R_WT * LinePS[14]) >> 8;
            }
            for (; X < Width; X++, LinePS += Channel)
            {
                LinePD[X] = (B_WT * LinePS[0] + G_WT * LinePS[1] + R_WT * LinePS[2]) >> 8;
            }
        }
    }
    else if (Channel == 1)
    {
        if (Output != Input)
        {
            memcpy(Output, Input, Height*

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