texture-synthesis 0.7.1

#![warn(clippy::all)]
#![warn(rust_2018_idioms)]

//! `texture-synthesis` is a light API for Multiresolution Stochastic Texture Synthesis,
//! a non-parametric example-based algorithm for image generation.
//!
//! First, you build a `Session` via a `SessionBuilder`, which follows the builder pattern. Calling
//! `build` on the SessionBuilder loads all of the input images and checks for various errors.
//!
//! `Session` has a `run()` method that takes all of the parameters and inputs added in the session
//! builder to generated an image, which is returned as a `GeneratedImage`.
//!
//! You can save, stream, or inspect the image from `GeneratedImage`.
//!
//! ## Features
//!
//! 1. Single example generation
//! 2. Multi example generation
//! 3. Guided synthesis
//! 4. Style transfer
//! 5. Inpainting
//! 6. Tiling textures
//!
//! Please, refer to the examples folder in the [repository](https://github.com/EmbarkStudios/texture-synthesis) for the features usage examples.
//!
//! ## Usage
//! Session follows a "builder pattern" for defining parameters, meaning you chain functions together.
//!
//! ```no_run
//! // Create a new session with default parameters
//! let session = texture_synthesis::Session::builder()
//!     // Set some parameters
//!     .seed(10)
//!     .nearest_neighbors(20)
//!     // Specify example images
//!     .add_example(&"imgs/1.jpg")
//!     // Build the session
//!     .build().expect("failed to build session");
//!
//! // Generate a new image
//! let generated_img = session.run(None);
//!
//! // Save the generated image to disk
//! generated_img.save("my_generated_img.jpg").expect("failed to save generated image");
//! ```
mod errors;
mod img_pyramid;
use img_pyramid::*;
mod utils;
use utils::*;
mod multires_stochastic_texture_synthesis;
use multires_stochastic_texture_synthesis::*;
use std::path::Path;
mod unsync;

pub use image;
pub use utils::{load_dynamic_image, ChannelMask, ImageSource};

pub use errors::Error;

#[derive(Copy, Clone)]
pub struct Dims {
    pub width: u32,
    pub height: u32,
}

impl Dims {
    pub fn square(size: u32) -> Self {
        Self {
            width: size,
            height: size,
        }
    }
    pub fn new(width: u32, height: u32) -> Self {
        Self { width, height }
    }
}

pub struct CoordinateTransform {
    buffer: Vec<u32>,
    dims: Dims,
    max_map_id: u32, // total number of maps required to perform transformation
}

impl<'a> CoordinateTransform {
    /// Applies the coordinate transformation from new source images. Important to ensure that you have same number and sizes of the images as during synthesis where the coordinate transform was saved from
    pub fn apply<E: Into<ImageSource<'a>>, I: IntoIterator<Item = E>>(
        &self,
        source: I,
    ) -> Result<image::RgbaImage, Error> {
        let ref_maps: Vec<image::RgbaImage> = source
            .into_iter()
            .map(|t| load_image(t.into(), None))
            .collect::<Result<Vec<_>, Error>>()?;
        //assert same number of maps
        if ref_maps.len() as u32 != self.max_map_id {
            return Err(Error::MapsCountMismatch(
                ref_maps.len() as u32,
                self.max_map_id,
            ));
        }
        //init new empty image
        let mut img = image::RgbaImage::new(self.dims.width, self.dims.height);
        // populate with pixels from ref maps
        for (i, pix) in img.pixels_mut().enumerate() {
            let x = self.buffer[i * 3];
            let y = self.buffer[i * 3 + 1];
            let map = self.buffer[i * 3 + 2];

            *pix = *ref_maps[map as usize].get_pixel(x, y);
        }

        Ok(img)
    }
}

struct Parameters {
    tiling_mode: bool,
    nearest_neighbors: u32,
    random_sample_locations: u64,
    cauchy_dispersion: f32,
    backtrack_percent: f32,
    backtrack_stages: u32,
    resize_input: Option<Dims>,
    output_size: Dims,
    guide_alpha: f32,
    random_resolve: Option<u64>,
    max_thread_count: Option<usize>,
    seed: u64,
}

impl Default for Parameters {
    fn default() -> Self {
        Self {
            tiling_mode: false,
            nearest_neighbors: 50,
            random_sample_locations: 50,
            cauchy_dispersion: 1.0,
            backtrack_percent: 0.5,
            backtrack_stages: 5,
            resize_input: None,
            output_size: Dims::square(500),
            guide_alpha: 0.8,
            random_resolve: None,
            max_thread_count: None,
            seed: 0,
        }
    }
}

impl Parameters {
    fn to_generator_params(&self) -> GeneratorParams {
        GeneratorParams {
            nearest_neighbors: self.nearest_neighbors,
            random_sample_locations: self.random_sample_locations,
            cauchy_dispersion: self.cauchy_dispersion,
            p: self.backtrack_percent,
            p_stages: self.backtrack_stages as i32,
            seed: self.seed,
            alpha: self.guide_alpha,
            max_thread_count: self.max_thread_count.unwrap_or_else(num_cpus::get),
            tiling_mode: self.tiling_mode,
        }
    }
}

/// An image generated by a `Session::run()`
pub struct GeneratedImage {
    inner: multires_stochastic_texture_synthesis::Generator,
}

impl GeneratedImage {
    /// Saves the generated image to the specified path
    pub fn save<P: AsRef<Path>>(&self, path: P) -> Result<(), Error> {
        let path = path.as_ref();
        if let Some(parent_path) = path.parent() {
            std::fs::create_dir_all(&parent_path)?;
        }

        self.inner.color_map.as_ref().save(&path)?;
        Ok(())
    }

    /// Writes the generated image to the specified stream
    pub fn write<W: std::io::Write>(
        self,
        writer: &mut W,
        fmt: image::ImageOutputFormat,
    ) -> Result<(), Error> {
        let dyn_img = self.into_image();
        Ok(dyn_img.write_to(writer, fmt)?)
    }

    /// Saves debug information such as copied patches ids, map ids (if you have multi example generation)
    /// and a map indicating generated pixels the generator was "uncertain" of.
    pub fn save_debug<P: AsRef<Path>>(&self, dir: P) -> Result<(), Error> {
        let dir = dir.as_ref();
        std::fs::create_dir_all(&dir)?;

        self.inner
            .get_uncertainty_map()
            .save(&dir.join("uncertainty.png"))?;
        let id_maps = self.inner.get_id_maps();
        id_maps[0].save(&dir.join("patch_id.png"))?;
        id_maps[1].save(&dir.join("map_id.png"))?;

        Ok(())
    }

    /// Get coordinate transform of this generated image, which can be repeated on a new image
    /// ```no_run
    /// use texture_synthesis as ts;
    ///  //create a new session
    /// let texsynth = ts::Session::builder()
    /// //load a single example image
    /// .add_example(&"imgs/1.jpg")
    /// .build().unwrap();
    /// //generate an image
    /// let generated = texsynth.run(None);
    /// //now we can repeat the same transformation on a different image
    /// let repeated_transform_image = generated.get_coordinate_transform().apply(&["imgs/2.jpg"]);
    /// ```
    pub fn get_coordinate_transform(&self) -> CoordinateTransform {
        self.inner.get_coord_transform()
    }

    /// Returns the generated output image
    pub fn into_image(self) -> image::DynamicImage {
        image::DynamicImage::ImageRgba8(self.inner.color_map.into_inner())
    }
}

impl AsRef<image::RgbaImage> for GeneratedImage {
    fn as_ref(&self) -> &image::RgbaImage {
        self.inner.color_map.as_ref()
    }
}

/// Method used for sampling an example image.
pub enum GenericSampleMethod<Img> {
    /// All pixels in the example image can be sampled.
    All,
    /// No pixels in the example image will be sampled.
    Ignore,
    /// Pixels are selectively sampled based on an image.
    Image(Img),
}

pub type SampleMethod<'a> = GenericSampleMethod<ImageSource<'a>>;
pub type SamplingMethod = GenericSampleMethod<image::RgbaImage>;

impl<Img> GenericSampleMethod<Img> {
    #[inline]
    fn is_ignore(&self) -> bool {
        match self {
            Self::Ignore => true,
            _ => false,
        }
    }
}

impl<'a, IS> From<IS> for SampleMethod<'a>
where
    IS: Into<ImageSource<'a>>,
{
    fn from(is: IS) -> Self {
        SampleMethod::Image(is.into())
    }
}

/// A builder for an `Example`
pub struct ExampleBuilder<'a> {
    img: ImageSource<'a>,
    guide: Option<ImageSource<'a>>,
    sample_method: SampleMethod<'a>,
}

impl<'a> ExampleBuilder<'a> {
    /// Creates a new example builder from the specified image source
    pub fn new<I: Into<ImageSource<'a>>>(img: I) -> Self {
        Self {
            img: img.into(),
            guide: None,
            sample_method: SampleMethod::All,
        }
    }

    /// Use a guide map that describe a 'FROM' transformation.
    ///
    /// Note: If any one example has a guide, then they **all** must have
    /// a guide, otherwise a session will not be created.
    pub fn with_guide<G: Into<ImageSource<'a>>>(mut self, guide: G) -> Self {
        self.guide = Some(guide.into());
        self
    }

    /// Specify how the example image is sampled during texture generation.
    ///
    /// By default, all pixels in the example can be sampled.
    pub fn set_sample_method<M: Into<SampleMethod<'a>>>(mut self, method: M) -> Self {
        self.sample_method = method.into();
        self
    }
}

impl<'a> Into<Example<'a>> for ExampleBuilder<'a> {
    fn into(self) -> Example<'a> {
        Example {
            img: self.img,
            guide: self.guide,
            sample_method: self.sample_method,
        }
    }
}

/// An example to be used in texture generation
pub struct Example<'a> {
    img: ImageSource<'a>,
    guide: Option<ImageSource<'a>>,
    sample_method: SampleMethod<'a>,
}

impl<'a> Example<'a> {
    /// Creates a new example builder from the specified image source
    pub fn builder<I: Into<ImageSource<'a>>>(img: I) -> ExampleBuilder<'a> {
        ExampleBuilder::new(img)
    }
    pub fn image_source(&self) -> &ImageSource<'a> {
        &self.img
    }
    /// Creates a new example input from the specified image source
    pub fn new<I: Into<ImageSource<'a>>>(img: I) -> Self {
        Self {
            img: img.into(),
            guide: None,
            sample_method: SampleMethod::All,
        }
    }

    /// Use a guide map that describe a 'FROM' transformation.
    ///
    /// Note: If any one example has a guide, then they **all** must have
    /// a guide, otherwise a session will not be created.
    pub fn with_guide<G: Into<ImageSource<'a>>>(&mut self, guide: G) -> &mut Self {
        self.guide = Some(guide.into());
        self
    }

    /// Specify how the example image is sampled during texture generation.
    ///
    /// By default, all pixels in the example can be sampled.
    pub fn set_sample_method<M: Into<SampleMethod<'a>>>(&mut self, method: M) -> &mut Self {
        self.sample_method = method.into();
        self
    }

    fn resolve(
        self,
        backtracks: u32,
        resize: Option<Dims>,
        target_guide: &Option<ImagePyramid>,
    ) -> Result<ResolvedExample, Error> {
        let image = ImagePyramid::new(load_image(self.img, resize)?, Some(backtracks));

        let guide = match target_guide {
            Some(tg) => {
                Some(match self.guide {
                    Some(exguide) => {
                        let exguide = load_image(exguide, resize)?;
                        ImagePyramid::new(exguide, Some(backtracks))
                    }
                    None => {
                        // if we do not have an example guide, create it as a b/w maps of the example
                        let mut gm = transform_to_guide_map(image.bottom().clone(), resize, 2.0);
                        match_histograms(&mut gm, tg.bottom());

                        ImagePyramid::new(gm, Some(backtracks))
                    }
                })
            }
            None => None,
        };

        let method = match self.sample_method {
            SampleMethod::All => SamplingMethod::All,
            SampleMethod::Ignore => SamplingMethod::Ignore,
            SampleMethod::Image(src) => {
                let img = load_image(src, resize)?;
                SamplingMethod::Image(img)
            }
        };

        Ok(ResolvedExample {
            image,
            guide,
            method,
        })
    }
}

impl<'a, IS> From<IS> for Example<'a>
where
    IS: Into<ImageSource<'a>>,
{
    fn from(is: IS) -> Self {
        Example::new(is)
    }
}

enum MaskOrImg<'a> {
    Mask(utils::ChannelMask),
    ImageSource(ImageSource<'a>),
}

struct InpaintMask<'a> {
    src: MaskOrImg<'a>,
    example_index: usize,
    dims: Dims,
}

/// Builds a session by setting parameters and adding input images, calling
/// `build` will check all of the provided inputs to verify that texture
/// synthesis will provide valid output
#[derive(Default)]
pub struct SessionBuilder<'a> {
    examples: Vec<Example<'a>>,
    target_guide: Option<ImageSource<'a>>,
    inpaint_mask: Option<InpaintMask<'a>>,
    params: Parameters,
}

impl<'a> SessionBuilder<'a> {
    /// Creates a new `SessionBuilder`, can also be created via `Session::builder()`
    pub fn new() -> Self {
        Self::default()
    }

    /// Adds an `Example` from which a generator will synthesize a new image.
    ///
    /// See [examples/01_single_example_synthesis](https://github.com/EmbarkStudios/texture-synthesis/tree/master/lib/examples/01_single_example_synthesis.rs)
    ///
    /// # Examples
    ///
    /// ```no_run
    /// let tex_synth = texture_synthesis::Session::builder()
    ///     .add_example(&"imgs/1.jpg")
    ///     .build().expect("failed to build session");
    /// ```
    pub fn add_example<E: Into<Example<'a>>>(mut self, example: E) -> Self {
        self.examples.push(example.into());
        self
    }

    /// Adds Examples from which a generator will synthesize a new image.
    ///
    /// See [examples/02_multi_example_synthesis](https://github.com/EmbarkStudios/texture-synthesis/tree/master/lib/examples/02_multi_example_synthesis.rs)
    ///
    /// # Examples
    ///
    /// ```no_run
    /// let tex_synth = texture_synthesis::Session::builder()
    ///     .add_examples(&[&"imgs/1.jpg", &"imgs/2.jpg"])
    ///     .build().expect("failed to build session");
    /// ```
    pub fn add_examples<E: Into<Example<'a>>, I: IntoIterator<Item = E>>(
        mut self,
        examples: I,
    ) -> Self {
        self.examples.extend(examples.into_iter().map(|e| e.into()));
        self
    }

    /// Inpaints an example. Due to how inpainting works, a size must also be provided, as
    /// all examples, as well as the inpaint mask, must be the same size as each other, as
    /// well as the final output image. Using `resize_input` or `output_size` is ignored
    /// if this method is called.
    ///
    /// To prevent sampling from the example, you can specify `SamplingMethod::Ignore` with `Example::set_sample_method`.
    ///
    /// See [examples/05_inpaint](https://github.com/EmbarkStudios/texture-synthesis/tree/master/lib/examples/05_inpaint.rs)
    ///
    /// # Examples
    ///
    /// ```no_run
    /// let tex_synth = texture_synthesis::Session::builder()
    ///     .add_examples(&[&"imgs/1.jpg", &"imgs/3.jpg"])
    ///     .inpaint_example(
    ///         &"masks/inpaint.jpg",
    ///         // This will prevent sampling from the imgs/2.jpg, note that
    ///         // we *MUST* provide at least one example to source from!
    ///         texture_synthesis::Example::builder(&"imgs/2.jpg")
    ///             .set_sample_method(texture_synthesis::SampleMethod::Ignore),
    ///         texture_synthesis::Dims::square(400)
    ///     )
    ///     .build().expect("failed to build session");
    /// ```
    pub fn inpaint_example<I: Into<ImageSource<'a>>, E: Into<Example<'a>>>(
        mut self,
        inpaint_mask: I,
        example: E,
        size: Dims,
    ) -> Self {
        self.inpaint_mask = Some(InpaintMask {
            src: MaskOrImg::ImageSource(inpaint_mask.into()),
            example_index: self.examples.len(),
            dims: size,
        });
        self.examples.push(example.into());
        self
    }

    /// Inpaints an example, using a specific channel in the example image as the inpaint mask
    ///
    /// # Examples
    ///
    /// ```no_run
    /// let tex_synth = texture_synthesis::Session::builder()
    ///     .inpaint_example_channel(
    ///         // Let's use inpaint the alpha channel
    ///         texture_synthesis::ChannelMask::A,
    ///         &"imgs/bricks.png",
    ///         texture_synthesis::Dims::square(400)
    ///     )
    ///     .build().expect("failed to build session");
    /// ```
    pub fn inpaint_example_channel<E: Into<Example<'a>>>(
        mut self,
        mask: utils::ChannelMask,
        example: E,
        size: Dims,
    ) -> Self {
        self.inpaint_mask = Some(InpaintMask {
            src: MaskOrImg::Mask(mask),
            example_index: self.examples.len(),
            dims: size,
        });
        self.examples.push(example.into());
        self
    }

    /// Loads a target guide map.
    ///
    /// If no `Example` guide maps are provided, this will produce a style transfer effect,
    /// where the Examples are styles and the target guide is content.
    ///
    /// See [examples/03_guided_synthesis](https://github.com/EmbarkStudios/texture-synthesis/tree/master/lib/examples/03_guided_synthesis.rs),
    /// or [examples/04_style_transfer](https://github.com/EmbarkStudios/texture-synthesis/tree/master/lib/examples/04_style_transfer.rs),
    pub fn load_target_guide<I: Into<ImageSource<'a>>>(mut self, guide: I) -> Self {
        self.target_guide = Some(guide.into());
        self
    }

    /// Overwrite incoming images sizes
    pub fn resize_input(mut self, dims: Dims) -> Self {
        self.params.resize_input = Some(dims);
        self
    }

    /// Changes pseudo-deterministic seed.
    /// Global structures will stay same, if same seed is provided, but smaller details may change due to undeterministic nature of multithreading.
    pub fn seed(mut self, value: u64) -> Self {
        self.params.seed = value;
        self
    }

    /// Makes the generator output tiling image.
    /// Default: false.
    pub fn tiling_mode(mut self, is_tiling: bool) -> Self {
        self.params.tiling_mode = is_tiling;
        self
    }

    /// How many neighboring pixels each pixel is aware of during the generation (bigger number -> more global structures are captured).
    /// Default: 50
    pub fn nearest_neighbors(mut self, count: u32) -> Self {
        self.params.nearest_neighbors = count;
        self
    }

    /// How many random locations will be considered during a pixel resolution apart from its immediate neighbors.
    /// If unsure, keep same as nearest neighbors.
    /// Default: 50
    pub fn random_sample_locations(mut self, count: u64) -> Self {
        self.params.random_sample_locations = count;
        self
    }

    /// Make first X pixels to be randomly resolved and prevent them from being overwritten.
    /// Can be an enforcing factor of remixing multiple images together.
    pub fn random_init(mut self, count: u64) -> Self {
        self.params.random_resolve = Some(count);
        self
    }

    /// The distribution dispersion used for picking best candidate (controls the distribution 'tail flatness').
    /// Values close to 0.0 will produce 'harsh' borders between generated 'chunks'. Values closer to 1.0 will produce a smoother gradient on those borders.
    /// For futher reading, check out P.Harrison's "Image Texture Tools".
    /// Default: 1.0
    pub fn cauchy_dispersion(mut self, value: f32) -> Self {
        self.params.cauchy_dispersion = value;
        self
    }

    /// Controls the trade-off between guide and example map.
    /// If doing style transfer, set to about 0.8-0.6 to allow for more global structures of the style.
    /// If you'd like the guide maps to be considered through all generation stages, set to 1.0 (which would prevent guide maps weight "decay" during the score calculation).
    /// Default: 0.8
    pub fn guide_alpha(mut self, value: f32) -> Self {
        self.params.guide_alpha = value;
        self
    }

    /// The percentage of pixels to be backtracked during each p_stage. Range (0,1).
    /// Default: 0.5
    pub fn backtrack_percent(mut self, value: f32) -> Self {
        self.params.backtrack_percent = value;
        self
    }

    /// Controls the number of backtracking stages. Backtracking prevents 'garbage' generation.
    /// Right now, the depth of image pyramid for multiresolution synthesis
    /// depends on this parameter as well.
    /// Default: 5
    pub fn backtrack_stages(mut self, stages: u32) -> Self {
        self.params.backtrack_stages = stages;
        self
    }

    /// Specify size of the generated image.
    /// Default: 500x500
    pub fn output_size(mut self, dims: Dims) -> Self {
        self.params.output_size = dims;
        self
    }

    /// Specify the maximum number of threads that will be spawned
    /// at any one time in parallel. This number is allowed to exceed
    /// the number of logical cores on the system, but it should
    /// generally be kept at or below that number.
    ///
    /// Default: The number of logical cores on this system.
    pub fn max_thread_count(mut self, count: usize) -> Self {
        self.params.max_thread_count = Some(count);
        self
    }

    /// Creates a `Session`, or returns an error if invalid parameters or input
    /// images were specified.
    pub fn build(mut self) -> Result<Session, Error> {
        self.check_parameters_validity()?;
        self.check_images_validity()?;

        struct InpaintExample {
            inpaint_mask: image::RgbaImage,
            color_map: image::RgbaImage,
            example_index: usize,
        }

        let (inpaint, out_size, in_size) = match self.inpaint_mask {
            Some(inpaint_mask) => {
                let dims = inpaint_mask.dims;
                let inpaint_img = match inpaint_mask.src {
                    MaskOrImg::ImageSource(img) => load_image(img, Some(dims))?,
                    MaskOrImg::Mask(mask) => {
                        let example_img = &mut self.examples[inpaint_mask.example_index].img;

                        let dynamic_img = utils::load_dynamic_image(example_img.clone())?;
                        let inpaint_src = ImageSource::Image(dynamic_img.clone());

                        // Replace the example image source so we don't load it twice
                        *example_img = ImageSource::Image(dynamic_img);

                        let inpaint_mask = load_image(inpaint_src, Some(dims))?;

                        utils::apply_mask(inpaint_mask, mask)
                    }
                };

                let color_map = load_image(
                    self.examples[inpaint_mask.example_index].img.clone(),
                    Some(dims),
                )?;

                (
                    Some(InpaintExample {
                        inpaint_mask: inpaint_img,
                        color_map,
                        example_index: inpaint_mask.example_index,
                    }),
                    dims,
                    Some(dims),
                )
            }
            None => (None, self.params.output_size, self.params.resize_input),
        };

        let target_guide = match self.target_guide {
            Some(tg) => {
                let tg_img = load_image(tg, Some(out_size))?;

                let num_guides = self.examples.iter().filter(|ex| ex.guide.is_some()).count();
                let tg_img = if num_guides == 0 {
                    transform_to_guide_map(tg_img, None, 2.0)
                } else {
                    tg_img
                };

                Some(ImagePyramid::new(
                    tg_img,
                    Some(self.params.backtrack_stages as u32),
                ))
            }
            None => None,
        };

        let example_len = self.examples.len();

        let mut examples = Vec::with_capacity(example_len);
        let mut guides = if target_guide.is_some() {
            Vec::with_capacity(example_len)
        } else {
            Vec::new()
        };
        let mut methods = Vec::with_capacity(example_len);

        for example in self.examples {
            let resolved = example.resolve(self.params.backtrack_stages, in_size, &target_guide)?;

            examples.push(resolved.image);

            if let Some(guide) = resolved.guide {
                guides.push(guide);
            }

            methods.push(resolved.method);
        }

        // Initialize generator based on availability of an inpaint_mask.
        let generator = match inpaint {
            None => Generator::new(out_size),
            Some(inpaint) => Generator::new_from_inpaint(
                out_size,
                inpaint.inpaint_mask,
                inpaint.color_map,
                inpaint.example_index,
            ),
        };

        let session = Session {
            examples,
            guides: target_guide.map(|tg| GuidesPyramidStruct {
                target_guide: tg,
                example_guides: guides,
            }),
            sampling_methods: methods,
            params: self.params,
            generator,
        };

        Ok(session)
    }

    fn check_parameters_validity(&self) -> Result<(), Error> {
        if self.params.cauchy_dispersion < 0.0 || self.params.cauchy_dispersion > 1.0 {
            return Err(Error::InvalidRange(errors::InvalidRange {
                min: 0.0,
                max: 1.0,
                value: self.params.cauchy_dispersion,
                name: "cauchy-dispersion",
            }));
        }

        if self.params.backtrack_percent < 0.0 || self.params.backtrack_percent > 1.0 {
            return Err(Error::InvalidRange(errors::InvalidRange {
                min: 0.0,
                max: 1.0,
                value: self.params.backtrack_percent,
                name: "backtrack-percent",
            }));
        }

        if self.params.guide_alpha < 0.0 || self.params.guide_alpha > 1.0 {
            return Err(Error::InvalidRange(errors::InvalidRange {
                min: 0.0,
                max: 1.0,
                value: self.params.guide_alpha,
                name: "guide-alpha",
            }));
        }

        if let Some(max_count) = self.params.max_thread_count {
            if max_count == 0 {
                return Err(Error::InvalidRange(errors::InvalidRange {
                    min: 1.0,
                    max: 1024.0,
                    value: max_count as f32,
                    name: "max-thread-count",
                }));
            }
        }

        if self.params.random_sample_locations == 0 {
            return Err(Error::InvalidRange(errors::InvalidRange {
                min: 1.0,
                max: 1024.0,
                value: self.params.random_sample_locations as f32,
                name: "m-rand",
            }));
        }

        Ok(())
    }

    fn check_images_validity(&self) -> Result<(), Error> {
        // We must have at least one example image to source pixels from
        let input_count = self
            .examples
            .iter()
            .filter(|ex| !ex.sample_method.is_ignore())
            .count();

        if input_count == 0 {
            return Err(Error::NoExamples);
        }

        // If we have more than one example guide, then *every* example
        // needs a guide
        let num_guides = self.examples.iter().filter(|ex| ex.guide.is_some()).count();
        if num_guides != 0 && self.examples.len() != num_guides {
            return Err(Error::ExampleGuideMismatch(
                self.examples.len() as u32,
                num_guides as u32,
            ));
        }

        Ok(())
    }
}

struct ResolvedExample {
    image: ImagePyramid,
    guide: Option<ImagePyramid>,
    method: SamplingMethod,
}

/// Texture synthesis session.
///
/// Calling `run()` will generate a new image and return it, consuming the session in the
/// process. You can provide a `GeneratorProgress` implementation to periodically get
/// updates with the currently generated image and the number of pixels that
/// have been resolved both in the current stage and globally
///
/// # Example
/// ```no_run
/// let tex_synth = texture_synthesis::Session::builder()
///     .seed(10)
///     .tiling_mode(true)
///     .add_example(&"imgs/1.jpg")
///     .build().expect("failed to build session");
///
/// let generated_img = tex_synth.run(None);
/// generated_img.save("my_generated_img.jpg").expect("failed to save image");
/// ```
pub struct Session {
    examples: Vec<ImagePyramid>,
    guides: Option<GuidesPyramidStruct>,
    sampling_methods: Vec<SamplingMethod>,
    generator: Generator,
    params: Parameters,
}

impl Session {
    /// Creates a new session with default parameters.
    pub fn builder<'a>() -> SessionBuilder<'a> {
        SessionBuilder::default()
    }

    /// Runs the generator and outputs a generated image.
    /// Now, only runs Multiresolution Stochastic Texture Synthesis.
    /// Might be interesting to include more algorithms in the future.
    pub fn run(mut self, progress: Option<Box<dyn GeneratorProgress>>) -> GeneratedImage {
        // random resolve
        // TODO: Instead of consuming the generator, we could instead make the
        // seed and random_resolve parameters, so that you could rerun the
        // generator with the same inputs
        if let Some(count) = self.params.random_resolve {
            let lvl = self.examples[0].pyramid.len();
            let imgs: Vec<_> = self
                .examples
                .iter()
                .map(|a| ImageBuffer::from(&a.pyramid[lvl - 1])) //take the blurriest image
                .collect();

            self.generator
                .resolve_random_batch(count as usize, &imgs, self.params.seed);
        }

        // run generator
        self.generator.main_resolve_loop(
            &self.params.to_generator_params(),
            &self.examples,
            progress,
            &self.guides,
            &self.sampling_methods,
        );

        GeneratedImage {
            inner: self.generator,
        }
    }
}

/// Helper struct for passing progress information to external callers
pub struct ProgressStat {
    /// The current amount of work that has been done
    pub current: usize,
    /// The total amount of work to do
    pub total: usize,
}

/// The current state of the image generator
pub struct ProgressUpdate<'a> {
    /// The currenty resolved image
    pub image: &'a image::RgbaImage,
    /// The total progress for the final image
    pub total: ProgressStat,
    /// The progress for the current stage
    pub stage: ProgressStat,
}

/// Allows the generator to update external callers with the current
/// progress of the image synthesis
pub trait GeneratorProgress {
    fn update(&mut self, info: ProgressUpdate<'_>);
}

impl<G> GeneratorProgress for G
where
    G: FnMut(ProgressUpdate<'_>) + Send,
{
    fn update(&mut self, info: ProgressUpdate<'_>) {
        self(info)
    }
}