serialimage/optimalexposure.rs
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#![warn(missing_docs)]
use std::time::Duration;
#[derive(Debug, Clone, PartialEq)]
/// Builder for the [`serialimage::OptimumExposure`] calculator.
///
/// The default values are:
/// * `percentile_pix` - 0.995
/// * `pixel_tgt` - 40000. / 65536.
/// * `pixel_uncertainty` - 5000. / 65536.
/// * `pixel_exclusion` - 100
/// * `min_allowed_exp` - 1 ms
/// * `max_allowed_exp` - 10 s
/// * `max_allowed_bin` - 1
pub struct OptimumExposureBuilder {
percentile_pix: f32,
pixel_tgt: f32,
pixel_uncertainty: f32,
pixel_exclusion: u32,
min_allowed_exp: Duration,
max_allowed_exp: Duration,
max_allowed_bin: u16,
}
impl Default for OptimumExposureBuilder {
fn default() -> Self {
Self::new()
}
}
impl OptimumExposureBuilder {
fn new() -> Self {
Self {
percentile_pix: 0.995,
pixel_tgt: 40000. / 65536.,
pixel_uncertainty: 5000. / 65536.,
pixel_exclusion: 100,
min_allowed_exp: Duration::from_millis(1),
max_allowed_exp: Duration::from_secs(10),
max_allowed_bin: 1,
}
}
/// Set the percentile of the pixel values to use as the target pixel value.
///
/// The pixels are sorted in ascending order and the pixel at the percentile
/// is targeted for optimization.
pub fn percentile_pix(mut self, percentile_pix: f32) -> Self {
self.percentile_pix = percentile_pix;
self
}
/// Set the target pixel value.
///
/// The target pixel value is the value that the algorithm will try to reach.
pub fn pixel_tgt(mut self, pixel_tgt: f32) -> Self {
self.pixel_tgt = pixel_tgt;
self
}
/// Set the uncertainty of the target pixel value.
///
/// The pixel value is considered to be within the target if it is within the
/// target value plus or minus the uncertainty.
pub fn pixel_uncertainty(mut self, pixel_uncertainty: f32) -> Self {
self.pixel_uncertainty = pixel_uncertainty;
self
}
/// Set the number of pixels to exclude from the top of the image.
///
/// The pixels are sorted in ascending order and the top `pixel_exclusion` pixels
/// are excluded from the optimization.
pub fn pixel_exclusion(mut self, pixel_exclusion: u32) -> Self {
self.pixel_exclusion = pixel_exclusion;
self
}
/// Set the minimum allowed exposure time.
///
/// The minimum allowed exposure time is the shortest exposure time that the
/// algorithm will consider.
pub fn min_allowed_exp(mut self, min_allowed_exp: Duration) -> Self {
self.min_allowed_exp = min_allowed_exp;
self
}
/// Set the maximum allowed exposure time.
///
/// The maximum allowed exposure time is the longest exposure time that the
/// algorithm will consider.
pub fn max_allowed_exp(mut self, max_allowed_exp: Duration) -> Self {
self.max_allowed_exp = max_allowed_exp;
self
}
/// Set the maximum allowed binning.
///
/// The maximum allowed binning is the largest binning factor that the algorithm
/// will consider to minimize the exposure time.
pub fn max_allowed_bin(mut self, max_allowed_bin: u16) -> Self {
self.max_allowed_bin = max_allowed_bin;
self
}
/// Build the [`serialimage::OptimumExposure`].
pub fn build(self) -> Result<OptimumExposure, &'static str> {
if !(1.6e-5f32..=1f32).contains(&self.pixel_tgt) {
return Err("Target pixel value must be between 1.6e-5 and 1");
}
if !(1.6e-5f32..=1f32).contains(&self.pixel_uncertainty) {
return Err("Pixel uncertainty must be between 1.6e-5 and 1");
}
if self.percentile_pix < 0f32 || self.percentile_pix > 1f32 {
return Err("Percentile must be between 0 and 1.");
}
if self.min_allowed_exp >= self.max_allowed_exp {
return Err("Minimum allowed exposure must be less than maximum allowed exposure");
}
if self.pixel_exclusion > 65536 {
return Err("Pixel exclusion must be less than 65536");
}
if self.max_allowed_bin > 32 {
return Err("Maximum allowed binning must be less than 32");
}
Ok(OptimumExposure {
percentile_pix: self.percentile_pix,
pixel_tgt: self.pixel_tgt,
pixel_uncertainty: self.pixel_uncertainty,
pixel_exclusion: self.pixel_exclusion,
min_allowed_exp: self.min_allowed_exp,
max_allowed_exp: self.max_allowed_exp,
max_allowed_bin: self.max_allowed_bin,
})
}
}
/// Configuration used to find the optimum exposure.
///
///
/// # Options
/// * `percentile_pix` - The percentile of the pixel values to use as the target pixel value, in fraction.
/// * `pixel_tgt` - The target pixel value, in fraction.
/// * `pixel_tol` - The uncertainty of the target pixel value, in fraction.
/// * `pixel_exclusion` - The number of pixels to exclude from the top of the image.
/// * `min_exposure` - The minimum allowed exposure time.
/// * `max_exposure` - The maximum allowed exposure time.
/// * `max_bin` - The maximum allowed binning.
///
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct OptimumExposure {
percentile_pix: f32,
pixel_tgt: f32,
pixel_uncertainty: f32,
min_allowed_exp: Duration,
max_allowed_exp: Duration,
max_allowed_bin: u16,
pixel_exclusion: u32,
}
impl OptimumExposure {
/// Find the optimum exposure time and binning to reach a target pixel value.
/// The algorithm does not use any hysteresis and uses simple scaling.
///
/// # Arguments
/// * `mut img` - The image luminance data as a vector of u16 that is consumed.
/// * `exposure` - The exposure duration used to obtain this image luminance data.
/// * `bin` - The binning used to obtain this image luminance data.
///
/// # Returns
/// * `Ok((Duration, u16))` - The optimum exposure time and binning.
///
/// # Errors
/// - Errors are returned as static string slices.
pub fn calculate(
&self,
mut img: Vec<u16>,
exposure: Duration,
bin: u8,
) -> Result<(Duration, u16), &'static str> {
let mut target_exposure;
let mut change_bin = true;
let pixel_tgt = self.pixel_tgt;
let pixel_uncertainty = self.pixel_uncertainty;
let percentile_pix = self.percentile_pix;
let min_allowed_exp = self.min_allowed_exp;
let max_allowed_exp = self.max_allowed_exp;
let max_allowed_bin = self.max_allowed_bin;
let pixel_exclusion = self.pixel_exclusion;
if !(1.6e-5f32..=1f32).contains(&pixel_tgt) {
return Err("Target pixel value must be between 1.6e-5 and 1");
}
if !(1.6e-5f32..=1f32).contains(&pixel_uncertainty) {
return Err("Pixel uncertainty must be between 1.6e-5 and 1");
}
if !(0f32..=1f32).contains(&percentile_pix) {
return Err("Percentile must be between 0 and 1");
}
if min_allowed_exp >= max_allowed_exp {
return Err("Minimum allowed exposure must be less than maximum allowed exposure");
}
if pixel_exclusion > img.len() as u32 {
return Err("Pixel exclusion must be less than the number of pixels");
}
let max_allowed_bin = if max_allowed_bin < 2 {
1
} else {
max_allowed_bin
};
let pixel_tgt = pixel_tgt * 65535f32;
let pixel_uncertainty = pixel_uncertainty * 65535f32;
if max_allowed_bin < 2 {
change_bin = false;
}
let mut bin = bin as u16;
img.sort();
let mut coord: usize;
if percentile_pix > 0.99999 {
coord = img.len() - 1_usize;
} else {
coord = (percentile_pix * (img.len() - 1) as f32).floor() as usize;
}
if coord < pixel_exclusion as usize {
coord = img.len() - 1 - pixel_exclusion as usize;
}
let imgvec = img.to_vec();
let val = imgvec.get(coord);
let val = match val {
Some(v) => *v as f64,
None => 1e-5_f64,
};
if (pixel_tgt as f64 - val).abs() < pixel_uncertainty as f64 {
return Ok((exposure, bin));
}
let val = {
if val <= 1e-5 {
1e-5
} else {
val
}
};
target_exposure = Duration::from_secs_f64(
(pixel_tgt as f64 * exposure.as_micros() as f64 * 1e-6 / val).abs(),
);
if change_bin {
let mut tgt_exp = target_exposure;
let mut bin_ = bin;
if tgt_exp < max_allowed_exp {
while tgt_exp < max_allowed_exp && bin_ > 2 {
bin_ /= 2;
tgt_exp *= 4;
}
} else {
while tgt_exp > max_allowed_exp && bin_ * 2 <= max_allowed_bin {
bin_ *= 2;
tgt_exp /= 4;
}
}
target_exposure = tgt_exp;
bin = bin_;
}
if target_exposure > max_allowed_exp {
target_exposure = max_allowed_exp;
}
if target_exposure < min_allowed_exp {
target_exposure = min_allowed_exp;
}
if bin < 1 {
bin = 1;
}
if bin > max_allowed_bin {
bin = max_allowed_bin;
}
Ok((target_exposure, bin))
}
/// Retrieve the builder for the [`serialimage::OptimumExposure`] calculator.
/// This is useful for changing the configuration of the calculator.
pub fn get_builder(&self) -> OptimumExposureBuilder {
OptimumExposureBuilder {
percentile_pix: self.percentile_pix,
pixel_tgt: self.pixel_tgt,
pixel_uncertainty: self.pixel_uncertainty,
pixel_exclusion: self.pixel_exclusion,
min_allowed_exp: self.min_allowed_exp,
max_allowed_exp: self.max_allowed_exp,
max_allowed_bin: self.max_allowed_bin,
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_optimum_exposure() {
let opt_exp = OptimumExposureBuilder::default()
.pixel_exclusion(1)
.build()
.unwrap();
let img = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
let exp = Duration::from_secs(10); // expected exposure
let bin = 1; // expected binning
let res = opt_exp.calculate(img, exp, bin).unwrap();
assert_eq!(res, (exp, bin as u16));
assert_eq!(
opt_exp.get_builder(),
OptimumExposureBuilder::default().pixel_exclusion(1)
);
}
}