Add gamma correction

A user requested this a while ago. This feature also ads contrast and
brightness correction. The code is fast!
This commit is contained in:
Kwabena W. Agyeman 2019-01-01 02:28:40 -05:00
parent b47dbe2c15
commit 8bcf5ac0c3
7 changed files with 152 additions and 0 deletions

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@ -0,0 +1,21 @@
# Gamma Correction
#
# This example shows off gamma correction to make the image brighter. The gamma
# correction method can also fix contrast and brightness too.
import sensor, image, time
sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)
sensor.skip_frames(time = 2000)
clock = time.clock()
while(True):
clock.tick()
# Gamma, contrast, and brightness correction are applied to each color channel. The
# values are scaled to the range per color channel per image type...
img = sensor.snapshot().gamma_corr(gamma = 0.5, contrast = 1.0, brightness = 0.0)
print(clock.fps())

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@ -189,3 +189,10 @@ float fast_log(float x)
{
return 0.69314718f * fast_log2 (x);
}
float fast_powf(float a, float b)
{
union { float d; int x; } u = { a };
u.x = (int)((b * (u.x - 1064866805)) + 1064866805);
return u.d;
}

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@ -20,6 +20,7 @@ float fast_cbrtf(float d);
float fast_fabsf(float d);
float fast_log(float x);
float fast_log2(float x);
float fast_powf(float a, float b);
extern const float cos_table[360];
extern const float sin_table[360];
#endif // __FMATH_H__

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@ -1296,6 +1296,7 @@ void imlib_close(image_t *img, int ksize, int threshold, image_t *mask);
void imlib_top_hat(image_t *img, int ksize, int threshold, image_t *mask);
void imlib_black_hat(image_t *img, int ksize, int threshold, image_t *mask);
// Math Functions
void imlib_gamma_corr(image_t *img, float gamma, float scale, float offset);
void imlib_negate(image_t *img);
void imlib_replace(image_t *img, const char *path, image_t *other, int scalar, bool hmirror, bool vflip, image_t *mask);
void imlib_add(image_t *img, const char *path, image_t *other, int scalar, image_t *mask);

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@ -6,6 +6,102 @@
#include "imlib.h"
#ifdef IMLIB_ENABLE_MATH_OPS
void imlib_gamma_corr(image_t *img, float gamma, float contrast, float brightness)
{
gamma = IM_DIV(1.0, gamma);
switch(img->bpp) {
case IMAGE_BPP_BINARY: {
float pScale = COLOR_BINARY_MAX - COLOR_BINARY_MIN;
float pDiv = 1 / pScale;
int *p_lut = fb_alloc((COLOR_BINARY_MAX - COLOR_BINARY_MIN + 1) * sizeof(int));
for (int i = COLOR_BINARY_MIN; i <= COLOR_BINARY_MAX; i++) {
int p = ((fast_powf(i * pDiv, gamma) * contrast) + brightness) * pScale;
p_lut[i] = IM_MIN(IM_MAX(p , COLOR_BINARY_MIN), COLOR_BINARY_MAX);
}
for (int y = 0, yy = img->h; y < yy; y++) {
uint32_t *data = IMAGE_COMPUTE_BINARY_PIXEL_ROW_PTR(img, y);
for (int x = 0, xx = img->w; x < xx; x++) {
int dataPixel = IMAGE_GET_BINARY_PIXEL_FAST(data, x);
int p = p_lut[dataPixel];
IMAGE_PUT_BINARY_PIXEL_FAST(data, x, p);
}
}
fb_free();
break;
}
case IMAGE_BPP_GRAYSCALE: {
float pScale = COLOR_GRAYSCALE_MAX - COLOR_GRAYSCALE_MIN;
float pDiv = 1 / pScale;
int *p_lut = fb_alloc((COLOR_GRAYSCALE_MAX - COLOR_GRAYSCALE_MIN + 1) * sizeof(int));
for (int i = COLOR_GRAYSCALE_MIN; i <= COLOR_GRAYSCALE_MAX; i++) {
int p = ((fast_powf(i * pDiv, gamma) * contrast) + brightness) * pScale;
p_lut[i] = IM_MIN(IM_MAX(p , COLOR_GRAYSCALE_MIN), COLOR_GRAYSCALE_MAX);
}
for (int y = 0, yy = img->h; y < yy; y++) {
uint8_t *data = IMAGE_COMPUTE_GRAYSCALE_PIXEL_ROW_PTR(img, y);
for (int x = 0, xx = img->w; x < xx; x++) {
int dataPixel = IMAGE_GET_GRAYSCALE_PIXEL_FAST(data, x);
int p = p_lut[dataPixel];
IMAGE_PUT_GRAYSCALE_PIXEL_FAST(data, x, p);
}
}
fb_free();
break;
}
case IMAGE_BPP_RGB565: {
float rScale = COLOR_R5_MAX - COLOR_R5_MIN;
float gScale = COLOR_G6_MAX - COLOR_G6_MIN;
float bScale = COLOR_B5_MAX - COLOR_B5_MIN;
float rDiv = 1 / rScale;
float gDiv = 1 / gScale;
float bDiv = 1 / bScale;
int *r_lut = fb_alloc((COLOR_R5_MAX - COLOR_R5_MIN + 1) * sizeof(int));
int *g_lut = fb_alloc((COLOR_G6_MAX - COLOR_G6_MIN + 1) * sizeof(int));
int *b_lut = fb_alloc((COLOR_B5_MAX - COLOR_B5_MIN + 1) * sizeof(int));
for (int i = COLOR_R5_MIN; i <= COLOR_R5_MAX; i++) {
int r = ((fast_powf(i * rDiv, gamma) * contrast) + brightness) * rScale;
r_lut[i] = IM_MIN(IM_MAX(r , COLOR_R5_MIN), COLOR_R5_MAX);
}
for (int i = COLOR_G6_MIN; i <= COLOR_G6_MAX; i++) {
int g = ((fast_powf(i * gDiv, gamma) * contrast) + brightness) * gScale;
g_lut[i] = IM_MIN(IM_MAX(g , COLOR_G6_MIN), COLOR_G6_MAX);
}
for (int i = COLOR_B5_MIN; i <= COLOR_B5_MAX; i++) {
int b = ((fast_powf(i * bDiv, gamma) * contrast) + brightness) * bScale;
b_lut[i] = IM_MIN(IM_MAX(b , COLOR_B5_MIN), COLOR_B5_MAX);
}
for (int y = 0, yy = img->h; y < yy; y++) {
uint16_t *data = IMAGE_COMPUTE_RGB565_PIXEL_ROW_PTR(img, y);
for (int x = 0, xx = img->w; x < xx; x++) {
int dataPixel = IMAGE_GET_RGB565_PIXEL_FAST(data, x);
int r = r_lut[COLOR_RGB565_TO_R5(dataPixel)];
int g = g_lut[COLOR_RGB565_TO_G6(dataPixel)];
int b = b_lut[COLOR_RGB565_TO_B5(dataPixel)];
IMAGE_PUT_RGB565_PIXEL_FAST(data, x, COLOR_R5_G6_B5_TO_RGB565(r, g, b));
}
}
fb_free();
fb_free();
fb_free();
break;
}
default: {
break;
}
}
}
void imlib_negate(image_t *img)
{
switch(img->bpp) {

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@ -1823,6 +1823,25 @@ STATIC mp_obj_t py_image_black_hat(uint n_args, const mp_obj_t *args, mp_map_t *
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(py_image_black_hat_obj, 2, py_image_black_hat);
STATIC mp_obj_t py_image_gamma_corr(uint n_args, const mp_obj_t *args, mp_map_t *kw_args)
{
image_t *arg_img =
py_helper_arg_to_image_mutable(args[0]);
float arg_gamma =
py_helper_keyword_float(n_args, args, 1, kw_args, MP_OBJ_NEW_QSTR(MP_QSTR_gamma), 1.0f);
float arg_contrast =
py_helper_keyword_float(n_args, args, 2, kw_args, MP_OBJ_NEW_QSTR(MP_QSTR_contrast), 1.0f);
float arg_brightness =
py_helper_keyword_float(n_args, args, 3, kw_args, MP_OBJ_NEW_QSTR(MP_QSTR_brightness), 0.0f);
fb_alloc_mark();
imlib_gamma_corr(arg_img, arg_gamma, arg_contrast, arg_brightness);
fb_alloc_free_till_mark();
return args[0];
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(py_image_gamma_corr_obj, 1, py_image_gamma_corr);
STATIC mp_obj_t py_image_negate(mp_obj_t img_obj)
{
fb_alloc_mark();
@ -5349,6 +5368,7 @@ static const mp_rom_map_elem_t locals_dict_table[] = {
{MP_ROM_QSTR(MP_QSTR_top_hat), MP_ROM_PTR(&py_image_top_hat_obj)},
{MP_ROM_QSTR(MP_QSTR_black_hat), MP_ROM_PTR(&py_image_black_hat_obj)},
/* Math Methods */
{MP_ROM_QSTR(MP_QSTR_gamma_corr), MP_ROM_PTR(&py_image_gamma_corr_obj)},
{MP_ROM_QSTR(MP_QSTR_negate), MP_ROM_PTR(&py_image_negate_obj)},
{MP_ROM_QSTR(MP_QSTR_replace), MP_ROM_PTR(&py_image_replace_obj)},
{MP_ROM_QSTR(MP_QSTR_add), MP_ROM_PTR(&py_image_add_obj)},

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@ -518,6 +518,12 @@ Q(black_hat)
// duplicate Q(threshold)
// duplicate Q(mask)
// Gamma Correct
Q(gamma_corr)
Q(gamma)
Q(contrast)
Q(brightness)
// Negate
Q(negate)