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tone equalizer: better mask autotune (for testing) #10014

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tone equalizer: better mask autotune (for testing) #10014

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6bd9bad
tone equalizer: better mask autotune
Mark-64 Sep 14, 2021
1cfec05
extended histogram [-10, +6] EV instead of [-8, +8] EV
Mark-64 Sep 17, 2021
074fa6b
revert to linear contrast, optitmize globally
Mark-64 Sep 17, 2021
09573fc
split auto-adjust formulas in two
Mark-64 Sep 18, 2021
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103 changes: 55 additions & 48 deletions src/iop/toneequal.c
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Expand Up @@ -1348,67 +1348,67 @@ static inline void build_interpolation_matrix(float A[CHANNELS * PIXEL_CHAN],


__DT_CLONE_TARGETS__
static inline void compute_log_histogram(const float *const restrict luminance,
static inline void compute_log_histogram_and_stats(const float *const restrict luminance,
int histogram[UI_SAMPLES],
const size_t num_elem,
int *max_histogram)
int *max_histogram,
float *first_decile, float *last_decile)
{
// (Re)init the histogram
memset(histogram, 0, sizeof(int) * UI_SAMPLES);

// we first calculate an extended histogram for better accuracy
#define TEMP_SAMPLES 2 * UI_SAMPLES
int temp_hist[TEMP_SAMPLES];
memset(temp_hist, 0, sizeof(int) * TEMP_SAMPLES);

// Split exposure in bins
#ifdef _OPENMP
#pragma omp parallel for default(none) schedule(simd:static) \
dt_omp_firstprivate(luminance, num_elem) \
reduction(+:histogram[:UI_SAMPLES])
reduction(+:temp_hist[:TEMP_SAMPLES])
#endif
for(size_t k = 0; k < num_elem; k++)
{
// the histogram shows bins between [-14; +2] EV remapped between [0 ; UI_SAMPLES[
const int index = CLAMP((int)(((log2f(luminance[k]) + 8.0f) / 8.0f) * (float)UI_SAMPLES), 0, UI_SAMPLES - 1);
histogram[index] += 1;
// extended histogram bins between [-10; +6] EV remapped between [0 ; 2 * UI_SAMPLES]
const int index = CLAMP((int)(((log2f(luminance[k]) + 10.0f) / 16.0f) * (float)TEMP_SAMPLES), 0, TEMP_SAMPLES - 1);
temp_hist[index] += 1;
}

*max_histogram = 0;

for(int k = 0; k < UI_SAMPLES; k++)
{
// store the max numbers of elements in bins for later normalization
if(histogram[k] > *max_histogram)
*max_histogram = histogram[k];
}
}


static inline void histogram_deciles(const int histogram[UI_SAMPLES], size_t hist_bins, size_t num_elem,
const float hist_span, const float hist_offset,
float *first_decile, float *last_decile)
{
// Browse an histogram of `hist_bins` bins containing a population of `num_elems` elements
// spanning from `hist_offset` to `hist_offset + hist_span`,
// looking for the position of the first and last deciles,
// and return their values scaled in the corresponding span

const int first = (int)((float)num_elem * 0.1f);
const int last = (int)((float)num_elem * 0.9f);
const int first = (int)((float)num_elem * 0.05f);
const int last = (int)((float)num_elem * 0.95f);
int population = 0;
int first_pos = 0;
int last_pos = 0;

// scout the histogram bins looking for deciles
for(size_t k = 0; k < hist_bins; ++k)
// scout the extended histogram bins looking for deciles
// these would not be accurate with the regular histogram
for(size_t k = 0; k < TEMP_SAMPLES; ++k)
{
const size_t prev_population = population;
population += histogram[k];
population += temp_hist[k];
if(prev_population < first && first <= population) first_pos = k;
if(prev_population < last && last <= population) last_pos = k;
}

// Convert bins positions to exposures
*first_decile = (hist_span * (((float)first_pos) / ((float)(hist_bins - 1)))) + hist_offset;
*last_decile = (hist_span * (((float)last_pos) / ((float)(hist_bins - 1)))) + hist_offset;
}
// Convert decile positions to exposures
*first_decile = 16.0 * (float)first_pos / (float)(TEMP_SAMPLES - 1) - 10.0;
*last_decile = 16.0 * (float)last_pos / (float)(TEMP_SAMPLES - 1) - 10.0;

*max_histogram = 0;
// remap the extended histogram into the normal one
// bins between [-8; 0] EV remapped between [0 ; UI_SAMPLES]
for(size_t k = 0; k < TEMP_SAMPLES; ++k)
{
float EV = 16.0 * (float)k / (float)(TEMP_SAMPLES - 1) - 10.0;
int i = CLAMP((int)(((EV + 8.0f) / 8.0f) * (float)UI_SAMPLES), 0, UI_SAMPLES - 1);
histogram[i] += temp_hist[k];

// store the max numbers of elements in bins for later normalization
if(histogram[i] > *max_histogram)
*max_histogram = histogram[i];
}
}

static inline void update_histogram(struct dt_iop_module_t *const self)
{
Expand All @@ -1419,9 +1419,8 @@ static inline void update_histogram(struct dt_iop_module_t *const self)
if(!g->histogram_valid && g->luminance_valid)
{
const size_t num_elem = g->thumb_preview_buf_height * g->thumb_preview_buf_width;
compute_log_histogram(g->thumb_preview_buf, g->histogram, num_elem, &g->max_histogram);
histogram_deciles(g->histogram, UI_SAMPLES, num_elem, 8.0f, -8.0f,
&g->histogram_first_decile, &g->histogram_last_decile);
compute_log_histogram_and_stats(g->thumb_preview_buf, g->histogram, num_elem, &g->max_histogram,
&g->histogram_first_decile, &g->histogram_last_decile);
g->histogram_average = (g->histogram_first_decile + g->histogram_last_decile) / 2.0f;
g->histogram_valid = TRUE;
}
Expand Down Expand Up @@ -1763,14 +1762,20 @@ static void auto_adjust_exposure_boost(GtkWidget *quad, gpointer user_data)
// to spread it over as many nodes as possible for better exposure control.
// Controls nodes are between -8 and 0 EV,
// so we aim at centering the exposure distribution on -4 EV
const float target = log2f(CONTRAST_FULCRUM);

dt_iop_gui_enter_critical_section(self);
g->histogram_valid = 0;
dt_iop_gui_leave_critical_section(self);

update_histogram(self);
p->exposure_boost += target - g->histogram_average;

const float fd_old = exp2f(g->histogram_first_decile);
const float ld_old = exp2f(g->histogram_last_decile);
const float s1 = CONTRAST_FULCRUM - exp2f(-7.0);
const float s2 = exp2f(-1.0) - CONTRAST_FULCRUM;
const float mix = fd_old * s2 + ld_old * s1;

p->exposure_boost += log2f(CONTRAST_FULCRUM * (s1 + s2) / mix);

// Update the GUI stuff
++darktable.gui->reset;
Expand Down Expand Up @@ -1821,19 +1826,21 @@ static void auto_adjust_contrast_boost(GtkWidget *quad, gpointer user_data)
return;
}

// The goal is to spread 80 % of the exposure histogram between -4 ± 3 EV
// The goal is to spread 90 % of the exposure histogram in the [-7, -1] EV
dt_iop_gui_enter_critical_section(self);
g->histogram_valid = 0;
dt_iop_gui_leave_critical_section(self);

const float target = log2f(CONTRAST_FULCRUM);
update_histogram(self);
const float span_left = fabsf(target - g->histogram_first_decile);
const float span_right = fabsf(g->histogram_last_decile - target);
const float origin = fmaxf(span_left, span_right);

// Compute the correction
p->contrast_boost = (3.0f - origin);
// calculate the corrections
const float fd_old = exp2f(g->histogram_first_decile);
const float ld_old = exp2f(g->histogram_last_decile);
const float s1 = CONTRAST_FULCRUM - exp2f(-7.0);
const float s2 = exp2f(-1.0) - CONTRAST_FULCRUM;
const float mix = fd_old * s2 + ld_old * s1;

p->contrast_boost += log2f(mix / (CONTRAST_FULCRUM * (ld_old - fd_old)));

// Update the GUI stuff
++darktable.gui->reset;
Expand Down Expand Up @@ -3251,7 +3258,7 @@ void gui_init(struct dt_iop_module_t *self)
g_signal_connect(G_OBJECT(g->exposure_boost), "quad-pressed", G_CALLBACK(auto_adjust_exposure_boost), self);

g->contrast_boost = dt_bauhaus_slider_from_params(self, "contrast_boost");
dt_bauhaus_slider_set_soft_range(g->contrast_boost, -4.0, 4.0);
dt_bauhaus_slider_set_soft_range(g->contrast_boost, -2.0, 2.0);
dt_bauhaus_slider_set_format(g->contrast_boost, "%+.2f EV");
gtk_widget_set_tooltip_text(g->contrast_boost, _("use this to counter the averaging effect of the guided filter\n"
"and dilate the mask contrast around -4EV\n"
Expand Down