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changed luminance calc to lut
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@elijahparker
elijahparker committed Sep 26, 2016
1 parent 6a668a7 commit 10ccce4
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Showing 2 changed files with 291 additions and 14 deletions.
107 changes: 93 additions & 14 deletions lib/jpeg-lum.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -9,11 +9,94 @@ unsigned int size;
unsigned int histogram[256];
unsigned int width;
unsigned int height;
double pixel;
double luminance;
double rgb;
double pixel;
double clipped;

#define LUT_LENGTH 33
struct lut_t {
double x;
double y;
};
lut_t lut[LUT_LENGTH] =
{
{4.793865/4, -7},
{4.793865/2, -6},
{4.793865, -5},
{6.056875, -4.66666666666667},
{7.697362, -4.33333333333333},
{9.780035, -4},
{12.092661, -3.66666666666667},
{15.089602, -3.33333333333333},
{18.683953, -3},
{23.421734, -2.66666666666667},
{28.643862, -2.33333333333333},
{35.019192, -2},
{42.607219, -1.66666666666667},
{52.126612, -1.33333333333333},
{63.956853, -1},
{76.885797, -0.666666666666667},
{89.6882, -0.333333333333333},
{103.382354, 0},
{118.336503, 0.333333333333333},
{135.244366, 0.666666666666667},
{147.969053, 1},
{162.615242, 1.33333333333333},
{182.654258, 1.66666666666667},
{194.224312, 2},
{206.764022, 2.33333333333333},
{213.891809, 2.66666666666667},
{230.007117, 3},
{238.483315, 3.33333333333333},
{246.258409, 3.66666666666667},
{249.447248, 4},
{249.495413, 4.33333333333333},
{252, 5},
{253, 6}
};

double lum(double x)
{
int i;

if(x < lut[0].x) return lut[0].y - 1;
if(x > lut[LUT_LENGTH-1].x) return lut[LUT_LENGTH-1].y + 1;

for( i = 0; i < LUT_LENGTH-1; i++ )
{
if ( lut[i].x <= x && lut[i+1].x >= x )
{
double diffx = x - lut[i].x;
double diffn = lut[i+1].x - lut[i].x;

return lut[i].y + ( lut[i+1].y - lut[i].y ) * diffx / diffn;
}
}
printf("error - not found\n");
return 0; // Not in Range
}


double lum(double x)
{
int i;

if(x < lut[0].x) return lut[0].y - 1;
if(x > lut[LUT_LENGTH-1].x) return lut[LUT_LENGTH-1].y + 1;

for( i = 0; i < LUT_LENGTH-1; i++ )
{
if ( lut[i].x <= x && lut[i+1].x >= x )
{
double diffx = x - lut[i].x;
double diffn = lut[i+1].x - lut[i].x;

return lut[i].y + ( lut[i+1].y - lut[i].y ) * diffx / diffn;
}
}

return 0; // Not in Range
}

int read_jpeg_file(char *filename)
{
Expand Down Expand Up @@ -41,26 +124,22 @@ int read_jpeg_file(char *filename)
unsigned long count = 0;
while (cinfo.output_scanline < cinfo.image_height) {
jpeg_read_scanlines( &cinfo, row_pointer, 1 );
for (i=0; i<cinfo.image_width;i++) {
for (i=0; i<cinfo.image_width;i+=cinfo.num_components) {
pixel = 0.0;
for(component=0;component<cinfo.num_components;component++) {
if(component < 2) {
rgb = (double) row_pointer[0][i + component];
rgb = pow(rgb / 255.0, 1.0 / 2.2) * 255.0; // convert to linear (remove gamma correction)
pixel += rgb;
pixel = (double) row_pointer[0][i + component];
pixel = lum(pixel);
if(pixel > 4) clipped++;
luminance += pixel;
count++;
// histogram[(int)pixel]++;
}
}
pixel /= 3.0;
if(pixel > 255.0) pixel = 255.0;
histogram[(int)pixel]++;
luminance += (pixel - 127.0) / (256.0 / 8.0);
count++;
}
}
luminance /= (double)count;
luminance /= 2.0;
luminance += 2.0;
clipped = (double)histogram[255] / (double)count;
clipped /= (double)count;
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
free(row_pointer[0]);
Expand Down
198 changes: 198 additions & 0 deletions lib/test.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,198 @@
#include <stdio.h>
#include <jpeglib.h>
#include <stdlib.h>
#include <unistd.h>
#include <cstring>
#include <math.h>

unsigned int size;
unsigned int histogram[256];
unsigned int width;
unsigned int height;
double luminance;
double pixel;
double clipped;

int read_jpeg_file(char *filename);

int main()
{

for(int i = 1; i<32; i++) {
char filename[64];
sprintf(filename, "thumb_thm%03d.jpg", i);
read_jpeg_file(filename);
printf("%f\n", luminance);
}
}


#define LUT_LENGTH 33
struct lut_t {
double x;
double y;
};
lut_t lut[LUT_LENGTH] =
{
{4.793865/4, -7},
{4.793865/2, -6},
{4.793865, -5},
{6.056875, -4.66666666666667},
{7.697362, -4.33333333333333},
{9.780035, -4},
{12.092661, -3.66666666666667},
{15.089602, -3.33333333333333},
{18.683953, -3},
{23.421734, -2.66666666666667},
{28.643862, -2.33333333333333},
{35.019192, -2},
{42.607219, -1.66666666666667},
{52.126612, -1.33333333333333},
{63.956853, -1},
{76.885797, -0.666666666666667},
{89.6882, -0.333333333333333},
{103.382354, 0},
{118.336503, 0.333333333333333},
{135.244366, 0.666666666666667},
{147.969053, 1},
{162.615242, 1.33333333333333},
{182.654258, 1.66666666666667},
{194.224312, 2},
{206.764022, 2.33333333333333},
{213.891809, 2.66666666666667},
{230.007117, 3},
{238.483315, 3.33333333333333},
{246.258409, 3.66666666666667},
{249.447248, 4},
{249.495413, 4.33333333333333},
{252, 5},
{253, 6}
};

double lum(double x)
{
int i;

if(x < lut[0].x) return lut[0].y - 1;
if(x > lut[LUT_LENGTH-1].x) return lut[LUT_LENGTH-1].y + 1;

for( i = 0; i < LUT_LENGTH-1; i++ )
{
if ( lut[i].x <= x && lut[i+1].x >= x )
{
double diffx = x - lut[i].x;
double diffn = lut[i+1].x - lut[i].x;

return lut[i].y + ( lut[i+1].y - lut[i].y ) * diffx / diffn;
}
}
printf("error - not found\n");
return 0; // Not in Range
}

int read_jpeg_file(char *filename)
{
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
JSAMPROW row_pointer[1];
FILE *infile = fopen(filename, "rb");
unsigned int i = 0, component = 0;
if (!infile) {
printf("Error opening jpeg file %s\n!", filename);
return -1;
}
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, infile);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);

width = cinfo.output_width;
height = cinfo.output_height;
luminance = 0.0;
size = cinfo.output_width*cinfo.output_height*cinfo.num_components*sizeof(unsigned int);
memset(histogram, 0, sizeof(int)*256);
row_pointer[0] = (unsigned char *)malloc(cinfo.output_width*cinfo.num_components);
unsigned long count = 0;
while (cinfo.output_scanline < cinfo.image_height) {
jpeg_read_scanlines( &cinfo, row_pointer, 1 );
for (i=0; i<cinfo.image_width;i+=cinfo.num_components) {
pixel = 0.0;
for(component=0;component<cinfo.num_components;component++) {
if(component < 2) {
pixel = (double) row_pointer[0][i + component];
pixel = lum(pixel);
if(pixel > 4) clipped++;
luminance += pixel;
count++;
// histogram[(int)pixel]++;
}
}
}
}
luminance /= (double)count;
clipped /= (double)count;
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
free(row_pointer[0]);
fclose(infile);
return 1;
}

/*
int read_jpeg_file(char *filename)
{
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
JSAMPROW row_pointer[1];
FILE *infile = fopen(filename, "rb");
unsigned int i = 0, component = 0;
if (!infile) {
printf("Error opening jpeg file %s\n!", filename);
return -1;
}
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, infile);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);
width = cinfo.output_width;
height = cinfo.output_height;
size = cinfo.output_width*cinfo.output_height*cinfo.num_components*sizeof(unsigned int);
row_pointer[0] = (unsigned char *)malloc(cinfo.output_width*cinfo.num_components);
unsigned long count = 0;
rgb[0] = 0.0;
rgb[1] = 0.0;
rgb[2] = 0.0;
while (cinfo.output_scanline < cinfo.image_height) {
jpeg_read_scanlines( &cinfo, row_pointer, 1 );
int black_row = 1;
for (i=0; i<cinfo.image_width*cinfo.num_components;i++) {
if(row_pointer[0][i]) {
black_row = 0;
break;
}
}
if(black_row) continue;
for (i=0; i<cinfo.image_width*cinfo.num_components;i+=cinfo.num_components) {
for(component=0;component<cinfo.num_components;component++) {
if(component < 3) {
rgb[component] += (double) row_pointer[0][i + component];
}
}
count++;
}
}
rgb[0] /= count;
rgb[1] /= count;
rgb[2] /= count;
double avg = (rgb[0] + rgb[1] + rgb[2]) / 3;
printf("%f\n", avg);
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
free(row_pointer[0]);
fclose(infile);
return 1;
}*/

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