cranpose-ui-graphics 0.0.60

//! Image bitmap primitives used by render backends.

use crate::{BlendMode, Color, Size};
use std::hash::{Hash, Hasher};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
use thiserror::Error;

static NEXT_IMAGE_BITMAP_ID: AtomicU64 = AtomicU64::new(1);

/// Errors returned while constructing an [`ImageBitmap`].
#[derive(Debug, Clone, PartialEq, Eq, Error)]
pub enum ImageBitmapError {
    #[error("image dimensions must be greater than zero")]
    InvalidDimensions,
    #[error("image dimensions are too large")]
    DimensionsTooLarge,
    #[error("pixel data length mismatch: expected {expected} bytes, got {actual}")]
    PixelDataLengthMismatch { expected: usize, actual: usize },
}

/// Immutable RGBA image data used by UI primitives and render backends.
#[derive(Clone, Debug)]
pub struct ImageBitmap {
    id: u64,
    width: u32,
    height: u32,
    pixels: Arc<[u8]>,
}

/// Simple image color filter model.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ColorFilter {
    /// Compose-style tint using `BlendMode::SrcIn`.
    Tint(Color),
    /// Explicit per-channel modulation (multiply behavior).
    Modulate(Color),
    /// 4x5 color matrix in row-major order.
    ///
    /// Rows map output RGBA channels, columns map input RGBA plus constant term:
    /// `out = M * [r, g, b, a, 1]`.
    Matrix([f32; 20]),
}

impl ColorFilter {
    /// Creates a Compose-style tint filter (`SrcIn`).
    pub fn tint(color: Color) -> Self {
        Self::Tint(color)
    }

    /// Creates an explicit modulation filter that multiplies channels by `color`.
    pub fn modulate(color: Color) -> Self {
        Self::Modulate(color)
    }

    /// Creates a filter from a 4x5 color matrix.
    pub fn matrix(matrix: [f32; 20]) -> Self {
        Self::Matrix(matrix)
    }

    pub fn compose(self, next: ColorFilter) -> ColorFilter {
        ColorFilter::Matrix(compose_color_matrices(self.as_matrix(), next.as_matrix()))
    }

    pub fn as_matrix(self) -> [f32; 20] {
        match self {
            Self::Tint(tint) => [
                0.0,
                0.0,
                0.0,
                tint.r(),
                0.0, // R' = A * tint.r
                0.0,
                0.0,
                0.0,
                tint.g(),
                0.0, // G' = A * tint.g
                0.0,
                0.0,
                0.0,
                tint.b(),
                0.0, // B' = A * tint.b
                0.0,
                0.0,
                0.0,
                tint.a(),
                0.0, // A' = A * tint.a
            ],
            Self::Modulate(modulate) => [
                modulate.r(),
                0.0,
                0.0,
                0.0,
                0.0, // R' = R * modulate.r
                0.0,
                modulate.g(),
                0.0,
                0.0,
                0.0, // G' = G * modulate.g
                0.0,
                0.0,
                modulate.b(),
                0.0,
                0.0, // B' = B * modulate.b
                0.0,
                0.0,
                0.0,
                modulate.a(),
                0.0, // A' = A * modulate.a
            ],
            Self::Matrix(matrix) => matrix,
        }
    }

    pub fn apply_rgba(self, rgba: [f32; 4]) -> [f32; 4] {
        apply_color_matrix(self.as_matrix(), rgba)
    }

    pub fn supports_gpu_vertex_modulation(self) -> bool {
        matches!(self, Self::Modulate(_))
    }

    pub fn gpu_vertex_tint(self) -> Option<[f32; 4]> {
        match self {
            Self::Modulate(tint) => Some([tint.r(), tint.g(), tint.b(), tint.a()]),
            _ => None,
        }
    }

    pub fn blend_mode(self) -> BlendMode {
        match self {
            Self::Tint(_) => BlendMode::SrcIn,
            Self::Modulate(_) => BlendMode::Modulate,
            Self::Matrix(_) => BlendMode::SrcOver,
        }
    }
}

fn apply_color_matrix(matrix: [f32; 20], rgba: [f32; 4]) -> [f32; 4] {
    let r = rgba[0];
    let g = rgba[1];
    let b = rgba[2];
    let a = rgba[3];
    [
        (matrix[0] * r + matrix[1] * g + matrix[2] * b + matrix[3] * a + matrix[4]).clamp(0.0, 1.0),
        (matrix[5] * r + matrix[6] * g + matrix[7] * b + matrix[8] * a + matrix[9]).clamp(0.0, 1.0),
        (matrix[10] * r + matrix[11] * g + matrix[12] * b + matrix[13] * a + matrix[14])
            .clamp(0.0, 1.0),
        (matrix[15] * r + matrix[16] * g + matrix[17] * b + matrix[18] * a + matrix[19])
            .clamp(0.0, 1.0),
    ]
}

fn compose_color_matrices(first: [f32; 20], second: [f32; 20]) -> [f32; 20] {
    let mut composed = [0.0f32; 20];
    for row in 0..4 {
        let row_base = row * 5;
        let s0 = second[row_base];
        let s1 = second[row_base + 1];
        let s2 = second[row_base + 2];
        let s3 = second[row_base + 3];
        let s4 = second[row_base + 4];

        composed[row_base] = s0 * first[0] + s1 * first[5] + s2 * first[10] + s3 * first[15];
        composed[row_base + 1] = s0 * first[1] + s1 * first[6] + s2 * first[11] + s3 * first[16];
        composed[row_base + 2] = s0 * first[2] + s1 * first[7] + s2 * first[12] + s3 * first[17];
        composed[row_base + 3] = s0 * first[3] + s1 * first[8] + s2 * first[13] + s3 * first[18];
        composed[row_base + 4] =
            s0 * first[4] + s1 * first[9] + s2 * first[14] + s3 * first[19] + s4;
    }
    composed
}

impl ImageBitmap {
    /// Creates a bitmap from tightly packed RGBA8 pixels.
    pub fn from_rgba8(width: u32, height: u32, pixels: Vec<u8>) -> Result<Self, ImageBitmapError> {
        Self::from_rgba8_slice(width, height, &pixels)
    }

    /// Creates a bitmap from tightly packed RGBA8 pixels.
    pub fn from_rgba8_slice(
        width: u32,
        height: u32,
        pixels: &[u8],
    ) -> Result<Self, ImageBitmapError> {
        if width == 0 || height == 0 {
            return Err(ImageBitmapError::InvalidDimensions);
        }
        let expected = (width as usize)
            .checked_mul(height as usize)
            .and_then(|value| value.checked_mul(4))
            .ok_or(ImageBitmapError::DimensionsTooLarge)?;

        if pixels.len() != expected {
            return Err(ImageBitmapError::PixelDataLengthMismatch {
                expected,
                actual: pixels.len(),
            });
        }

        Ok(Self {
            id: NEXT_IMAGE_BITMAP_ID.fetch_add(1, Ordering::Relaxed),
            width,
            height,
            pixels: Arc::from(pixels),
        })
    }

    /// Stable bitmap identity used by caches.
    pub fn id(&self) -> u64 {
        self.id
    }

    /// Width in pixels.
    pub fn width(&self) -> u32 {
        self.width
    }

    /// Height in pixels.
    pub fn height(&self) -> u32 {
        self.height
    }

    /// Returns the raw RGBA8 pixel data.
    pub fn pixels(&self) -> &[u8] {
        &self.pixels
    }

    /// Returns intrinsic size in logical units.
    pub fn intrinsic_size(&self) -> Size {
        Size {
            width: self.width as f32,
            height: self.height as f32,
        }
    }
}

impl PartialEq for ImageBitmap {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id
    }
}

impl Eq for ImageBitmap {}

impl Hash for ImageBitmap {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.id.hash(state);
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn from_rgba8_accepts_valid_data() {
        let bitmap = ImageBitmap::from_rgba8(2, 1, vec![255, 0, 0, 255, 0, 255, 0, 255])
            .expect("valid bitmap");

        assert_eq!(bitmap.width(), 2);
        assert_eq!(bitmap.height(), 1);
        assert_eq!(bitmap.pixels().len(), 8);
    }

    #[test]
    fn from_rgba8_rejects_zero_dimensions() {
        let err = ImageBitmap::from_rgba8(0, 2, vec![]).expect_err("must fail");
        assert_eq!(err, ImageBitmapError::InvalidDimensions);
    }

    #[test]
    fn from_rgba8_rejects_wrong_pixel_length() {
        let err = ImageBitmap::from_rgba8(2, 2, vec![0; 15]).expect_err("must fail");
        assert_eq!(
            err,
            ImageBitmapError::PixelDataLengthMismatch {
                expected: 16,
                actual: 15,
            }
        );
    }

    #[test]
    fn from_rgba8_slice_accepts_valid_data() {
        let pixels = [255u8, 0, 0, 255];
        let bitmap = ImageBitmap::from_rgba8_slice(1, 1, &pixels).expect("valid bitmap");
        assert_eq!(bitmap.pixels(), &pixels);
    }

    #[test]
    fn ids_are_unique() {
        let a = ImageBitmap::from_rgba8(1, 1, vec![0, 0, 0, 255]).expect("bitmap a");
        let b = ImageBitmap::from_rgba8(1, 1, vec![0, 0, 0, 255]).expect("bitmap b");
        assert_ne!(a.id(), b.id());
    }

    #[test]
    fn intrinsic_size_matches_dimensions() {
        let bitmap = ImageBitmap::from_rgba8(3, 4, vec![255; 3 * 4 * 4]).expect("bitmap");
        assert_eq!(bitmap.intrinsic_size(), Size::new(3.0, 4.0));
    }

    #[test]
    fn tint_filter_multiplies_channels() {
        let filter = ColorFilter::modulate(Color::from_rgba_u8(128, 255, 64, 128));
        let tinted = filter.apply_rgba([1.0, 0.5, 1.0, 1.0]);
        assert!((tinted[0] - (128.0 / 255.0)).abs() < 1e-5);
        assert!((tinted[1] - 0.5).abs() < 1e-5);
        assert!((tinted[2] - (64.0 / 255.0)).abs() < 1e-5);
        assert!((tinted[3] - (128.0 / 255.0)).abs() < 1e-5);
    }

    #[test]
    fn tint_constructor_matches_variant() {
        let color = Color::from_rgba_u8(10, 20, 30, 40);
        assert_eq!(ColorFilter::tint(color), ColorFilter::Tint(color));
    }

    #[test]
    fn tint_filter_uses_src_in_behavior() {
        let filter = ColorFilter::tint(Color::from_rgba_u8(255, 128, 0, 128));
        let tinted = filter.apply_rgba([0.2, 0.4, 0.8, 0.25]);
        assert!((tinted[0] - 0.25).abs() < 1e-5);
        assert!((tinted[1] - (0.25 * 128.0 / 255.0)).abs() < 1e-5);
        assert!(tinted[2].abs() < 1e-5);
        assert!((tinted[3] - (0.25 * 128.0 / 255.0)).abs() < 1e-5);
    }

    #[test]
    fn matrix_filter_transforms_channels() {
        let matrix = [
            1.0, 0.0, 0.0, 0.0, 0.1, // R + 0.1
            0.0, 0.5, 0.0, 0.0, 0.0, // G * 0.5
            0.0, 0.0, 0.0, 1.0, 0.0, // A -> B
            0.0, 0.0, 0.0, 1.0, 0.0, // A passthrough
        ];
        let filter = ColorFilter::matrix(matrix);
        let transformed = filter.apply_rgba([0.2, 0.6, 0.9, 0.4]);
        assert!((transformed[0] - 0.3).abs() < 1e-5);
        assert!((transformed[1] - 0.3).abs() < 1e-5);
        assert!((transformed[2] - 0.4).abs() < 1e-5);
        assert!((transformed[3] - 0.4).abs() < 1e-5);
    }

    #[test]
    fn filter_compose_applies_in_order() {
        let first = ColorFilter::modulate(Color::from_rgba_u8(128, 255, 255, 255));
        let second = ColorFilter::tint(Color::from_rgba_u8(255, 0, 0, 255));
        let chained = first.compose(second);
        let direct_second = second.apply_rgba(first.apply_rgba([0.8, 0.4, 0.2, 0.5]));
        let composed = chained.apply_rgba([0.8, 0.4, 0.2, 0.5]);
        assert!((direct_second[0] - composed[0]).abs() < 1e-5);
        assert!((direct_second[1] - composed[1]).abs() < 1e-5);
        assert!((direct_second[2] - composed[2]).abs() < 1e-5);
        assert!((direct_second[3] - composed[3]).abs() < 1e-5);
    }
}