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//! The interface between images and the display.

/// The number of brightness levels for greyscale images (ie, 10).
pub const BRIGHTNESSES : usize = 10;

/// The maximum brightness level for greyscale images (ie, 9; the minimum is 0).
pub const MAX_BRIGHTNESS : u8 = (BRIGHTNESSES as u8)-1;


/// A trait providing the information that [`Display`] needs to render an image.
///
/// [`Display`]: crate::display::Display
///
/// # Example implementation
///
/// Here's an example of a 5×5 image type, using one byte for each 'pixel':
///
/// ```
/// # use tiny_led_matrix::Render;
/// struct GreyscaleImage (
///     [[u8; 5]; 5]
/// );
///
/// impl GreyscaleImage {
///     const fn new(data: &[[u8; 5]; 5]) -> GreyscaleImage {
///         GreyscaleImage(*data)
///     }
/// }
///
/// impl Render for GreyscaleImage {
///     fn brightness_at(&self, x: usize, y: usize) -> u8 {
///         self.0[y][x]
///     }
/// }
/// const GREY_HEART: GreyscaleImage = GreyscaleImage::new(&[
///     [0, 9, 0, 9, 0],
///     [9, 5, 9, 5, 9],
///     [9, 5, 5, 5, 9],
///     [0, 9, 5, 9, 0],
///     [0, 0, 9, 0, 0],
/// ]);
/// ```


pub trait Render {

    /// Returns the brightness value for a single LED.
    ///
    /// The ranges for the x and y coordinates are 0..IMAGE_COLS and
    /// 0..IMAGE_ROWS, as defined by the [`Matrix`] for the [`Display`]'s
    /// [`Frame`].
    ///
    /// (0, 0) is the top left.
    ///
    /// The result must be in the range 0..=[`MAX_BRIGHTNESS`]
    ///
    /// # Panics
    ///
    /// If the provided coordinates are out of range, may panic or return an
    /// arbitrary in-range result.
    ///
    /// [`Display`]: crate::display::Display
    /// [`Matrix`]: crate::display::Matrix
    /// [`Frame`]: crate::display::Frame
    fn brightness_at(&self, x: usize, y: usize) -> u8;

}