图片文档倾斜矫正算法 附完整c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*Stride);
        }
    }
}

void CPUImageColorInvertFilter(unsigned char* Input, unsigned char* Output, int  Width, int  Height, int Stride)
{
    int Channels = Stride / Width; unsigned char invertMap[256] = { 0 };
    for (int pixel = 0; pixel < 256; pixel++)
    {
        invertMap[pixel] = (255 - pixel);
    }
    if (Channels == 1) {
        for (int Y = 0; Y < Height; Y++)
        {
            unsigned char*     pOutput = Output + (Y * Stride);
            unsigned char*     pInput = Input + (Y * Stride);
            for (int X = 0; X < Width; X++)
            {
                pOutput[X] = invertMap[pInput[X]];
            }
        }
    }
    else
    {

        for (int Y = 0; Y < Height; Y++)
        {
            unsigned char*     pOutput = Output + (Y * Stride);
            unsigned char*     pInput = Input + (Y * Stride);
            for (int X = 0; X < Width; X++)
            {
                pOutput[0] = invertMap[pInput[0]];
                pOutput[1] = invertMap[pInput[1]];
                pOutput[2] = invertMap[pInput[2]];
                pInput += Channels;
                pOutput += Channels;
            }
        }
    }
}
float  CPUImageCalcSkewAngle(unsigned char* Input, int Width, int Height, cpu_rect *CheckRectPtr, int maxSkewToDetect, int stepsPerDegree, int localPeakRadius, int nLineCount)
{
    cpu_rect CheckRect = *CheckRectPtr;
    //确定指定的区域在原图片范围内
    CheckRect.x = clamp(CheckRect.x, 0, Width - 1);
    CheckRect.y = clamp(CheckRect.y, 0, Height - 1);
    CheckRect.Width = clamp(CheckRect.Width, 1, Width - 1);
    CheckRect.Height = clamp(CheckRect.Height, 1, Height - 1);

    // 处理参数
    maxSkewToDetect = clamp(maxSkewToDetect, 0, 91);
    localPeakRadius = clamp(localPeakRadius, 1, 10);
    stepsPerDegree = clamp(stepsPerDegree, 1, 10);
    int    houghHeight = (2 * maxSkewToDetect * stepsPerDegree);
    float    thetaStep = (2 * maxSkewToDetect * M_PI / 180) / houghHeight;
    int halfWidth = Width >> 1;
    int halfHeight = Height >> 1;
    // 计算 Hough 映射宽度
    int halfHoughWidth = (int)sqrtf((float)(halfWidth * halfWidth + halfHeight * halfHeight));
    int houghWidth = (halfHoughWidth * 2);
    float minTheta = 90.0f - maxSkewToDetect;
    unsigned short * houghMap = (unsigned short *)calloc(houghHeight*houghWidth, sizeof(unsigned short));
    float* sinMap = (float*)malloc(houghHeight * sizeof(float));
    float* cosMap = (float*)malloc(houghHeight * sizeof(float));
    cpu_HoughLine* HoughLines = (cpu_HoughLine*)calloc(houghHeight*houghWidth, sizeof(cpu_HoughLine));
    if (houghMap == NULL || sinMap == NULL || cosMap == NULL || HoughLines == NULL)
    {
        if (houghMap)
        {
            free(houghMap);
            houghMap = NULL;
        }
        if (sinMap)
        {
            free(sinMap);
            sinMap = NULL;
        }
        if (cosMap)
        {
            free(cosMap);
            cosMap = NULL;
        }
        if (HoughLines)
        {
            free(HoughLines);
            HoughLines = NULL;
        }
        return 0.0f;
    }
    else
    {
        // 预计算 Sin 与 Cos表
        float mt = (minTheta * M_PI / 180.0f);
        for (int i = 0; i < houghHeight; i++)
        {
            float cur_weight = mt + (i * thetaStep);
            sinMap[i] = fastSin(cur_weight);
            cosMap[i] = fastCos(cur_weight);
        }
    }
    int startX = -halfWidth + CheckRect.x;
    int startY = -halfHeight + CheckRect.y;
    int stopX = Width - halfWidth - (Width - CheckRect.Width);
    int stopY = Height - halfHeight - (Height - CheckRect.Height) - 1;
    int offset = Width - CheckRect.Width;


    unsigned char* src = Input + CheckRect.y *  Width + CheckRect.x;
    unsigned char* srcBelow = src + Width;

    for (int Y = startY; Y < stopY; Y++)
    {
        for (int X = startX; X < stopX; X++, src++, srcBelow++)
        {
            if ((*src < 128) && (*srcBelow >= 128))
            {
                for (int theta = 0; theta < houghHeight; theta++)
                {
                    int radius = (int)(cosMap[theta] * X - sinMap[theta] * Y) + halfHoughWidth;

                    if ((radius < 0) || (radius >= houghWidth))
                    {
                        continue;
                    }

                    houghMap[theta*houghWidth + radius]++;
                }
            }
        }
        src += offset;
        srcBelow += offset;
    }


    // 找到 Hough映射的最大值
    float maxMapIntensity = 0.0000000001f;
    for (int theta = 0; theta < houghHeight; theta++)
    {
        unsigned short * houghMapLine = houghMap + theta*houghWidth;
        for (int radius = 0; radius < houghWidth; radius++)
        {
            maxMapIntensity = max(maxMapIntensity, houghMapLine[radius]);
        }
    }
    int minLineIntensity = Width / 10;

    // 收集大于或等于指定强度的直线

    int lineIntensity = 0;
    bool foundGreater = false;
    int lineSize = 0;
    for (int theta = 0; theta < houghHeight; theta++)
    {
        unsigned short * houghMapLine = houghMap + theta*houghWidth;
        for (int radius = 0; radius < houghWidth; radius++)
        {
            // 取当前强度
            lineIntensity = houghMapLine[radius];

            if (lineIntensity < minLineIntensity)
            {
                continue;
            }

            foundGreater = false;

            // 检查邻边
            for (int t = theta - localPeakRadius, ttMax = theta + localPeakRadius; t < ttMax; t++)
            {
                //跳过map值
                if (t < 0)
                {
                    continue;
                }
                if (t >= houghHeight)
                {
                    break;
                }

                //如果不是局部最大则跳出
                if (foundGreater == true)
                {
                    break;
                }
                for (int r = radius - localPeakRadius, trMax = radius + localPeakRadius; r < trMax; r++)
                {
                    //跳过map值
                    if (r < 0)
                    {
                        continue;
                    }
                    if (r >= houghWidth)
                    {
                        break;
                    }
                    // 当前值与邻边对比
                    if (houghMap[t*houghWidth + r] > lineIntensity)
                    {
                        foundGreater = true;
                        break;
                    }
                }
            }
            // 可能是局部最大值,记录下来
            if (!foundGreater)
            {
                cpu_HoughLine tempVar;
                tempVar.Theta = 90.0f - maxSkewToDetect + (theta) / stepsPerDegree;
                tempVar.Radius = (radius - halfHoughWidth);
                tempVar.Intensity = lineIntensity;
                tempVar.RelativeIntensity = lineIntensity / maxMapIntensity;
                HoughLines[lineSize] = tempVar;
                lineSize++;
            }
        }
    }

    float skewAngle = 0;
    if (lineSize > 0)
    {
        //排序，从大到小 
        cpu_HoughLine temp;
        for (int i = 0; i < lineSize; i++)
        {
            for (int j = 0; j < lineSize - 1; j++)
            {
                if (HoughLines[j].Intensity < HoughLines[j + 1].Intensity)
                {
                    temp = HoughLines[j + 1];
                    HoughLines[j + 1] = HoughLines[j];
                    HoughLines[j] = temp;
                }
            }
        }

        int n = min(nLineCount, lineSize);

        float sumIntensity = 0;

        for (int i = 0; i < n; i++)
        {
            if (HoughLines[i].RelativeIntensity > 0.5f)
            {
                skewAngle += (HoughLines[i].Theta * HoughLines[i].RelativeIntensity);
                sumIntensity += HoughLines[i].RelativeIntensity;
            }
        }
        skewAngle = skewAngle / sumIntensity;
    }
    if (houghMap)
    {
        free(houghMap);
        houghMap = NULL;
    }
    if (sinMap)
    {
        free(sinMap);
        sinMap = NULL;
    }
    if (cosMap)
    {
        free(cosMap);
        cosMap = NULL;
    }
    if (HoughLines)
    {
        free(HoughLines);
        HoughLines = NULL;
    }
    if (skewAngle != 0)
    {
        return skewAngle - 90.0f;
    }
    return skewAngle;
}

void CPUImageRotateBilinear(unsigned char * Input, int Width, int Height, int Stride, unsigned char * Output, int outWidth, int outHeight, float angle, bool keepSize, int fillColorR, int fillColorG, int fillColorB)
{
    if (Input == NULL || Output == NULL) return;

    float  oldXradius = (float)(Width - 1) / 2;
    float  oldYradius = (float)(Height - 1) / 2;

    // 输出图像的半径大小

    float  newXradius = (float)(outWidth - 1) / 2;
    float  newYradius = (float)(outHeight - 1) / 2;

    // 角度的正弦和余弦
    float angleRad = -angle * M_PI / 180.0f;
    float angleCos = fastCos(angleRad);
    float angleSin = fastSin(angleRad);
    int Channels = Stride / Width;
    int dstOffset = outWidth*Channels - ((Channels == 1) ? outWidth : outWidth * Channels);

    // 背景色
    unsigned char fillR = fillColorR;
    unsigned char fillG = fillColorG;
    unsigned char fillB = fillColorB;
    // 临界点
    int lastHeight = Height - 1;
    int lastWidth = Width - 1;
    // 四点指针   
    unsigned char* src = (unsigned char*)Input;
    unsigned char* dst = (unsigned char*)Output;
    // cx, cy  目标像素的相对于图像中心的坐标 
    if (Channels == 1)
    {
        float cy = -newYradius;
        for (int y = 0; y < outHeight; y++)
        {
            const     float    tx = angleSin * cy + oldXradius;
            const float    ty = angleCos * cy + oldYradius;

            float cx = -newXradius;
            for (int x = 0; x < outWidth; x++, dst++)
            {
                // 初始起点位置
                const     float    ox = tx + angleCos * cx;
                const     float    oy = ty - angleSin * cx;

                const int    ox1 = (int)ox;
                const int    oy1 = (int)oy;

                // 判断是否为有效区域 
                if ((ox1 < 0) || (oy1 < 0) || (ox1 >= Width) || (oy1 >= Height))
                {
                    // 无效区域填充背景 
                    *dst = fillG;
                }
                else
                {
                    // 边界点处理 
                    const int    ox2 = (ox1 == lastWidth) ? ox1 : ox1 + 1;
                    const int    oy2 = (oy1 == lastHeight) ? oy1 : oy1 + 1;
                    float dx1 = ox - (float)ox1;
                    if (dx1 < 0)
                        dx1 = 0;
                    const     float dx2 = 1.0f - dx1;
                    float dy1 = oy - (float)oy1;
                    if (dy1 < 0)
                        dy1 = 0;
                    const     float dy2 = 1.0f - dy1;

                    unsigned char*p1 = src + oy1 * Stride;
                    unsigned char*    p2 = src + oy2 * Stride;
                    // 进行四点插值
                    *dst = (unsigned char)(
                        dy2 * (dx2 * p1[ox1] + dx1 * p1[ox2]) +
                        dy1 * (dx2 * p2[ox1] + dx1 * p2[ox2]));
                }
                cx++;
            }
            cy++;
            dst += dstOffset;
        }
    }
    else
    {
        float cy = -newYradius;
        for (int y = 0; y < outHeight; y++)
        {
            const     float     tx = angleSin * cy + oldXradius;
            const     float     ty = angleCos * cy + oldYradius;

            float cx = -newXradius;
            for (int x = 0; x < outWidth; x++, dst += Channels)
            {
                // 初始起点位置
                const     float ox = tx + angleCos * cx;
                const     float oy = ty - angleSin * cx;
                const int    ox1 = (int)ox;
                const int    oy1 = (int)oy;

                // 判断是否为有效区域 
                if ((ox1 < 0) || (oy1 < 0) || (ox1 >= Width) || (oy1 >= Height))
                {
                    // 无效区域填充背景 
                    dst[0] = fillR;
                    dst[1] = fillG;
                    dst[2] = fillB;
                }
                else
                {
                    // 边界点处理 
                    const int    ox2 = (ox1 == lastWidth) ? ox1 : ox1 + 1;
                    const int    oy2 = (oy1 == lastHeight) ? oy1 : oy1 + 1;
                    float dx1 = ox - (float)ox1;
                    if (dx1 < 0)
                        dx1 = 0;
                    const    float dx2 = 1.0f - dx1;
                    float dy1 = oy - (float)oy1;
                    if (dy1 < 0)
                        dy1 = 0;
                    const    float    dy2 = 1.0f - dy1;

                    // 计算四点的坐标
                    unsigned char*    p1 = src + oy1 * Stride;
                    unsigned char*  p2 = p1;
                    p1 += ox1 * Channels;
                    p2 += ox2 * Channels;

                    unsigned char* p3 = src + oy2 * Stride;
                    unsigned char* p4 = p3;
                    p3 += ox1 * Channels;
                    p4 += ox2 * Channels;

                    // 进行四点插值
                    dst[0] = (unsigned char)(
                        dy2 * (dx2 * p1[0] + dx1 * p2[0]) +
                        dy1 * (dx2 * p3[0] + dx1 * p4[0]));
                    dst[1] = (unsigned char)(
                        dy2 * (dx2 * p1[1] + dx1 * p2[1]) +
                        dy1 * (dx2 * p3[1] + dx1 * p4[1]));
                    dst[2] = (unsigned char)(
                        dy2 * (dx2 * p1[2] + dx1 * p2[2]) +
                        dy1 * (dx2 * p3[2] + dx1 * p4[2]));
                }
                cx++;
            }
            cy++;
            dst += dstOffset;
        }
    }
}

bool CPUImageIsTextImage(unsigned char * Input, int Width, int Height)
{
    const int blacklimit = 20;
    const int greylimit = 140;
    const int contrast_offset = 80;

    int prev_color[256];
    int cur_color[256];

    for (int i = 0; i < 256; i++)
    {
        cur_color[i] = 0;
        prev_color[i] = 0;
    }

    for (int i = 0; i <= blacklimit; i++)
    {
        //黑色
        cur_color[i] = 100;
        prev_color[i] = 100000;
    }

    for (int i = blacklimit + 1 + contrast_offset; i <= greylimit; i++)
    {
        //灰色
        cur_color[i] = 10;
        prev_color[i] = 10000;
    }

    for (int i = greylimit + 1 + contrast_offset; i <= 255; i++)
    {
        //白色
        cur_color[i] = 1;
        prev_color[i] = 1000;
    }
    int line_count = 0;


    int n = -1;
    for (int y = 0; y < Height; y += 10)
    {
        n++;
        int    white_amt = 0;
        unsigned char *  buffer = Input + y*Width;
        int x = 0;
        for (x = 1; x < Width; x++)
        {
            const unsigned char     prev_pixel = buffer[(x - 1)];
            const unsigned char     cur_pixel = buffer[x];

            if ((prev_color[prev_pixel]) && (cur_color[cur_pixel]))
            {
                //是否是白色
                if ((prev_color[prev_pixel] + cur_color[cur_pixel]) == 1001)
                {
                    white_amt++;
                }
            }
        }
        //白色的一行
        if (((float)white_amt / (float)x) > 0.85f)
        {
            line_count++;
        }
    }

    float line_count_ratio = (n != 0.f) ? (float)line_count / (float)n : 0.0f;

    if (line_count_ratio < 0.4f || line_count_ratio > 1.0f)
    {
        return false;
    }

    return true;
}

bool     CPUImageDocumentDeskew(unsigned char * Input, unsigned char *Output, int Width, int Height, int Stride)
{
    if (Input == NULL || Output == NULL || Input == Output)
        return false;
    int Channels = Stride / Width;
    //最大倾斜角度 
    int maxSkewToDetect = 89;

    cpu_rect rect = { 0 };
    rect.Width = Width;
    rect.Height = Height;
    // 以最大权重的2条直线为基准计算倾斜角度
    int nLineCount = 2;
    //角度步进数
    int stepsPerDegree = 1;
    //局部临界半径
    int localPeakRadius = 10;
    CPUImageGrayscaleFilter(Input, Output, Width, Height, Stride);
    if (!CPUImageIsTextImage(Output, Width, Height))
    {
        CPUImageColorInvertFilter(Output, Output, Width, Height, Width);
    }
    float skewAngle = CPUImageCalcSkewAngle(Output, Width, Height, &rect, maxSkewToDetect, stepsPerDegree, localPeakRadius, nLineCount);
    if ((skewAngle == 0) || (skewAngle < -maxSkewToDetect || skewAngle >   maxSkewToDetect))
    {
        memcpy(Output, Input, Height* Stride * sizeof(unsigned char));
        return false;
    }
    else
    {
        CPUImageRotateBilinear(Input, Width, Height, Stride, Output, Width, Height, -skewAngle, true, 255, 255, 255);
    }
    return true;
}


//分割路径函数
void splitpath(const char* path, char* drv, char* dir, char* name, char* ext)
{
    const char* end;
    const char* p;
    const char* s;
    if (path[0] && path[1] == ':') {
        if (drv) {
            *drv++ = *path++;
            *drv++ = *path++;
            *drv = '\0';
        }
    }
    else if (drv)
        *drv = '\0';
    for (end = path; *end && *end != ':';)
        end++;
    for (p = end; p > path && *--p != '\\' && *p != '/';)
        if (*p == '.') {
            end = p;
            break;
        }
    if (ext)
        for (s = end; (*ext = *s++);)
            ext++;
    for (p = end; p > path;)
        if (*--p == '\\' || *p == '/') {
            p++;
            break;
        }
    if (name) {
        for (s = p; s < end;)
            *name++ = *s++;
        *name = '\0';
    }
    if (dir) {
        for (s = path; s < p;)
            *dir++ = *s++;
        *dir = '\0';
    }
}

//取当前传入的文件位置
void getCurrentFilePath(const char *filePath, char *saveFile)
{
    char drive[_MAX_DRIVE];
    char dir[_MAX_DIR];
    char fname[_MAX_FNAME];
    char ext[_MAX_EXT];
    splitpath(filePath, drive, dir, fname, ext);
    int n = strlen(filePath);
    memcpy(saveFile, filePath, n);
    char * cur_saveFile = saveFile + (n - strlen(ext));
    cur_saveFile[0] = '_';
    cur_saveFile[1] = 0;
}

int main(int argc, char **argv)
{
    printf("Image Processing \n ");
    printf("博客:http://tntmonks.cnblogs.com/ \n ");
    printf("支持解析如下图片格式: \n ");
    printf("JPG, PNG, TGA, BMP, PSD, GIF, HDR, PIC \n ");

    //检查参数是否正确

    if (argc < 2)
    {
        printf("参数错误。 \n ");
        printf("请拖放文件到可执行文件上，或使用命令行：imageProc.exe 图片 \n ");
        printf("请拖放文件例如: imageProc.exe d:\\image.jpg \n ");

        return 0;
    }

    char*szfile = argv[1];
    //检查输入的文件是否存在
    if (_access(szfile, 0) == -1)
    {
        printf("输入的文件不存在，参数错误！ \n ");
    }

    getCurrentFilePath(szfile, saveFile);

    int Width = 0;                    //图片宽度
    int Height = 0;                   //图片高度
    int Channels = 0;                 //图片通道数
    unsigned char *inputImage = NULL; //输入图片指针
    double startTime = now();
    //加载图片
    inputImage = loadImage(szfile, &Width, &Height, &Channels);

    double nLoadTime = calcElapsed(startTime, now());
    printf("加载耗时: %d 毫秒!\n ", (int)(nLoadTime * 1000));
    if ((Channels != 0) && (Width != 0) && (Height != 0))
    {
        //分配与载入同等内存用于处理后输出结果
        unsigned char *outputImg = (unsigned char *)stbi__malloc(Width * Channels * Height * sizeof(unsigned char));
        if (inputImage)
        {
            //如果图片加载成功，则将内容复制给输出内存，方便处理
            memcpy(outputImg, inputImage, Width * Channels * Height);
        }
        else
        {
            printf("加载文件: %s 失败!\n ", szfile);
        }
        startTime = now();
        //处理算法
        CPUImageDocumentDeskew(inputImage, outputImg, Width, Height, Width*Channels);
        double nProcessTime = calcElapsed(startTime, now());
        printf("处理耗时: %d 毫秒!\n ", (int)(nProcessTime * 1000));
        //保存处理后的图片
        startTime = now();

        saveImage("_done.jpg", Width, Height, Channels, outputImg);
        double nSaveTime = calcElapsed(startTime, now());

        printf("保存耗时: %d 毫秒!\n ", (int)(nSaveTime * 1000));
        //释放占用的内存
        if (outputImg)
        {
            stbi_image_free(outputImg);
            outputImg = NULL;
        }

        if (inputImage)
        {
            stbi_image_free(inputImage);
            inputImage = NULL;
        }
    }
    else
    {
        printf("加载文件: %s 失败!\n", szfile);
    }

    getchar();
    printf("按任意键退出程序 \n");

    return EXIT_SUCCESS;
}