主要的算法函数实现如下:
复制代码
void LocalColorCorrection(unsigned char *Input, unsigned char *Output, int Width, int Height, int Channels) {
unsigned char *Mask = (unsigned char *) malloc(Width * Height * sizeof(unsigned char));
if (Mask == NULL)
return;
unsigned char LocalLut[256 * 256];
for (int mask = 0; mask < 256; ++mask) {
unsigned char *pLocalLut = LocalLut + (mask << 8);
for (int pix = 0; pix < 256; ++pix) {
pLocalLut[pix] = ClampToByte(255.0f * powf(pix / 255.0f, powf(2.0f, (128.0f - mask) / 128.0f)));
}
}
InvertGrayscale(Input, Output, Width, Height, Channels);
int Radius = (MAX(Width, Height) / 512) + 1;
BoxBlurGrayscale(Output, Mask, Width, Height, Radius);
for (int Y = 0; Y < Height; Y++) {
unsigned char *pOutput = Output + (Y * Width * Channels);
unsigned char *pInput = Input + (Y * Width * Channels);
unsigned char *pMask = Mask + (Y * Width);
for (int X = 0; X < Width; X++) {
unsigned char *pLocalLut = LocalLut + (pMask[X] << 8);
for (int C = 0; C < Channels; C++) {
pOutput[C] = pLocalLut[pInput[C]];
}
pOutput += Channels;
pInput += Channels;
}
}
free(Mask);
}
复制代码
做了一些算法性能上的优化,720P,1080P下实时没半点问题。
至于进一步优化性能和效果,就留待下回分解,
当然有没有下回,得看心情。
附完整C代码:
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/**
*implmentation of Local Color Correction using Non-Linear Masking published by Nathan Moroney Hewlett-Packard Laboratories, Palo Alto, California.
**/
#include "browse.h"
#define USE_SHELL_OPEN
#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
#include
#include
#include "timing.h"
#include
#include
#ifndef _MAX_DRIVE
#define _MAX_DRIVE 3
#endif
#ifndef _MAX_FNAME
#define _MAX_FNAME 256
#endif
#ifndef _MAX_EXT
#define _MAX_EXT 256
#endif
#ifndef _MAX_DIR
#define _MAX_DIR 256
#endif
#ifndef MIN
#define MIN(a, b) ( (a) > (b) ? (b) : (a) )
#endif
#ifndef MAX
#define MAX(a, b) (((a) > (b)) ? (a) : (b))
#endif
char saveFile[1024];
unsigned char *loadImage(const char *filename, int *Width, int *Height, int *Channels) {
return (stbi_load(filename, Width, Height, Channels, 0));
}
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;
if (!tje_encode_to_file(saveFile, Width, Height, Channels, true, Output)) {
fprintf(stderr, "save JPEG fail. ");
return;
}
#ifdef USE_SHELL_OPEN
browse(saveFile);
#endif
}
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 = '';
}
} else if (drv)
*drv = '';
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 = '';
}
if (dir) {
for (s = path; s < p;)
*dir++ = *s++;
*dir = '';
}
}
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);
size_t n = strlen(filePath);
memcpy(saveFile, filePath, n);
char *cur_saveFile = saveFile + (n - strlen(ext));
cur_saveFile[0] = '_';
cur_saveFile[1] = 0;
}
int GetMirrorPos(int Length, int Pos) {
if (Pos < 0)
return -Pos;
else if (Pos >= Length)
return Length + Length - Pos - 2;
else
return Pos;
}
unsigned char ClampToByte(int Value) {
if (Value < 0)
return 0;
else if (Value > 255)
return 255;
else
return (unsigned char) Value;
}
void FillLeftAndRight_Mirror(int *Array, int Length, int Radius) {
for (int X = 0; X < Radius; X++) {
Array[X] = Array[Radius + Radius - X];
Array[Radius + Length + X] = Array[Radius + Length - X - 2];
}
}
int SumOfArray(const int *Array, int Length) {
int Sum = 0;
for (int X = 0; X < Length; X++) {
Sum += Array[X];
}
return Sum;
}
void BoxBlurGrayscale(unsigned char *input, unsigned char *output, int Width, int Height, int Radius) {
if ((input == NULL) || (output == NULL)) return;
if ((Width <= 0) || (Height <= 0) || (Radius <= 0)) return;
if (Radius < 1) return;
Radius = MIN(MIN(Radius, Width - 1), Height - 1);
int SampleAmount = (2 * Radius + 1) * (2 * Radius + 1);
float Inv = 1.0f / SampleAmount;
int *ColValue = (int *) malloc((Width + Radius + Radius) * sizeof(int));
int *ColOffset = (int *) malloc((Height + Radius + Radius) * sizeof(int));
if ((ColValue == NULL) || (ColOffset == NULL)) {
if (ColValue != NULL) free(ColValue);
if (ColOffset != NULL) free(ColOffset);
return;
}
for (int Y = 0; Y < Height + Radius + Radius; Y++)
ColOffset[Y] = GetMirrorPos(Height, Y - Radius);
{
for (int Y = 0; Y < Height; Y++) {
unsigned char *scanLineOut = output + Y * Width;
if (Y == 0) {
memset(ColValue + Radius, 0, Width * sizeof(int));
for (int Z = -Radius; Z <= Radius; Z++) {
unsigned char *scanLineIn = input + ColOffset[Z + Radius] * Width;
for (int X = 0; X < Width; X++) {
ColValue[X + Radius] += scanLineIn[X];
}
}
} else {
unsigned char *RowMoveOut = input + ColOffset[Y - 1] * Width;
unsigned char *RowMoveIn = input + ColOffset[Y + Radius + Radius] * Width;
for (int X = 0; X < Width; X++) {
ColValue[X + Radius] -=
RowMoveOut[X] - RowMoveIn[X];
}
}
FillLeftAndRight_Mirror(ColValue, Width, Radius);
int LastSum = SumOfArray(ColValue, Radius * 2 + 1);
scanLineOut[0] = ClampToByte((int) (LastSum * Inv));
for (int X = 0 + 1; X < Width; X++) {
int NewSum = LastSum - ColValue[X - 1] + ColValue[X + Radius + Radius];
scanLineOut[X] = ClampToByte((int) (NewSum * Inv));
LastSum = NewSum;
}
}
}
free(ColValue);
free(ColOffset);
}
void InvertGrayscale(unsigned char *Input, unsigned char *Output, int Width, int Height, int Channels) {
if (Channels == 1) {
for (unsigned int Y = 0; Y < Height; Y++) {
unsigned char *pOutput = Output + (Y * Width);
unsigned char *pInput = Input + (Y * Width);
for (unsigned int X = 0; X < Width; X++) {
pOutput[X] = (unsigned char) (255 - pInput[X]);
}
}
} else {
for (unsigned int Y = 0; Y < Height; Y++) {
unsigned char *pOutput = Output + (Y * Width);
unsigned char *pInput = Input + (Y * Width * Channels);
for (unsigned int X = 0; X < Width; X++) {
pOutput[X] = (unsigned char) (255 - ClampToByte(
(21842 * pInput[0] + 21842 * pInput[1] + 21842 * pInput[2]) >> 16));
pInput += Channels;
}
}
}
}
void LocalColorCorrection(unsigned char *Input, unsigned char *Output, int Width, int Height, int Channels) {
unsigned char *Mask = (unsigned char *) malloc(Width * Height * sizeof(unsigned char));
if (Mask == NULL)
return;
unsigned char LocalLut[256 * 256];
for (int mask = 0; mask < 256; ++mask) {
unsigned char *pLocalLut = LocalLut + (mask << 8);
for (int pix = 0; pix < 256; ++pix) {
pLocalLut[pix] = ClampToByte(255.0f * powf(pix / 255.0f, powf(2.0f, (128.0f - mask) / 128.0f)));
}
}
InvertGrayscale(Input, Output, Width, Height, Channels);
int Radius = (MAX(Width, Height) / 512) + 1;
BoxBlurGrayscale(Output, Mask, Width, Height, Radius);
for (int Y = 0; Y < Height; Y++) {
unsigned char *pOutput = Output + (Y * Width * Channels);
unsigned char *pInput = Input + (Y * Width * Channels);
unsigned char *pMask = Mask + (Y * Width);
for (int X = 0; X < Width; X++) {
unsigned char *pLocalLut = LocalLut + (pMask[X] << 8);
for (int C = 0; C < Channels; C++) {
pOutput[C] = pLocalLut[pInput[C]];
}
pOutput += Channels;
pInput += Channels;
}
}
free(Mask);
}
int main(int argc, char **argv) {
printf("Local Color Correction demo ");
printf("blog:http://cpuimage.cnblogs.com/ ");
if (argc < 2) {
printf("usage: %s image ", argv[0]);
printf("eg: %s d:\image.jpg ", argv[0]);
return (0);
}
char *szfile = argv[1];
getCurrentFilePath(szfile, saveFile);
int Width = 0;
int Height = 0;
int Channels = 0;
unsigned char *inputImage = NULL;
double startTime = now();
inputImage = loadImage(szfile, &Width, &Height, &Channels);
double nLoadTime = calcElapsed(startTime, now());
printf("load time: %d ms. ", (int) (nLoadTime * 1000));
if ((Channels != 0) && (Width != 0) && (Height != 0)) {
unsigned char *outputImg = (unsigned char *) stbi__malloc(Width * Channels * Height * sizeof(unsigned char));
if (inputImage) {
memcpy(outputImg, inputImage, (size_t) (Width * Channels * Height));
} else {
printf("load: %s fail! ", szfile);
}
startTime = now();
LocalColorCorrection(inputImage, outputImg, Width, Height, Channels);
double nProcessTime = calcElapsed(startTime, now());
printf("process time: %d ms. ", (int) (nProcessTime * 1000));
startTime = now();
saveImage("done.jpg", Width, Height, Channels, outputImg);
double nSaveTime = calcElapsed(startTime, now());
printf("save time: %d ms. ", (int) (nSaveTime * 1000));
if (outputImg) {
stbi_image_free(outputImg);
}
if (inputImage) {
stbi_image_free(inputImage);
}
} else {
printf("load: %s fail! ", szfile);
}
getchar();
printf("press any key to exit. ");
return (EXIT_SUCCESS);
}
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