draw text

Cargo.toml

@@ -11,11 +11,12 @@ exclude = ["tdata", "benches/", ".gitignore"]
 [dependencies]
 mattr = "0.0.2"
 png = { version = "0.17", features = ["unstable"], optional = true }
+fontdue = { version = "0.7.3", optional = true }
 vecto = "0.1.0"
+umath = "0.0.7"
 
 [dev-dependencies]
-iai = { version = "0.1.1", features = [
+iai = { path = "../iai" }
-], git = "https://github.com/bend-n/iai/" }
 
 [[bench]]
 name = "overlays"
@@ -39,7 +40,8 @@ harness = false
 
 [features]
 save = ["png"]
-default = ["save"]
+text = ["fontdue"]
+default = ["save", "text"]
 
 [profile.release]
 debug = 2

README.md

@@ -16,3 +16,4 @@ quick simple image operations
 - [x] thick line drawing
 - [x] polygon drawing
 - [x] circle drawing
+- [x] text drawing

src/drawing/mod.rs

@@ -1,6 +1,10 @@
-//! contains drawing operations, like {line, box, triangle, polygon, circle} drawing
+//! contains drawing operations, like
+//! {line, box, triangle, polygon, circle, text}
+//! drawing
 mod r#box;
 mod circle;
 mod line;
 mod poly;
+#[cfg(feature = "text")]
+mod text;
 mod tri;

src/drawing/text.rs

@@ -0,0 +1,88 @@
+//! text raster
+
+use crate::Image;
+use fontdue::{layout::TextStyle, Font};
+use umath::FFloat;
+
+impl<T: AsMut<[u8]> + AsRef<[u8]>> Image<T, 4> {
+    /// Draw text.
+    ///
+    /// ```
+    /// # use fimg::Image;
+    /// let font = fontdue::Font::from_bytes(
+    /// &include_bytes!("../../tdata/CascadiaCode.ttf")[..],
+    /// 	fontdue::FontSettings {
+    /// 		scale: 200.0,
+    /// 		..Default::default()
+    /// 	},
+    /// ).unwrap();
+    /// let mut i: Image<_, 4> = Image::alloc(750, 250).boxed();
+    /// i.text(50, 10, 200.0, &font, "hello", [0, 0, 0, 255]);
+    /// assert_eq!(i.buffer(), include_bytes!("../../tdata/text.imgbuf"));
+    /// ```
+    pub fn text(&mut self, x: u32, y: u32, size: f32, font: &Font, text: &str, color: [u8; 4]) {
+        let mut lay =
+            fontdue::layout::Layout::new(fontdue::layout::CoordinateSystem::PositiveYDown);
+        lay.append(&[font], &TextStyle::new(text, size, 0));
+        for glpyh in lay.glyphs() {
+            let (metrics, bitmap) = font.rasterize(glpyh.parent, size);
+            for i in 0..metrics.width {
+                for j in 0..metrics.height {
+                    // SAFETY: the rasterizer kinda promises that metrics width and height are in bounds
+                    let fg = [color[0], color[1], color[2], unsafe {
+                        *bitmap.get_unchecked(j * metrics.width + i)
+                    }];
+                    let x = x + i as u32 + glpyh.x as u32;
+                    if x >= self.width() {
+                        continue;
+                    }
+                    let y = y + j as u32 + glpyh.y as u32;
+                    if y >= self.height() {
+                        continue;
+                    }
+                    // SAFETY: we clampin
+                    let bg = unsafe { self.pixel_mut(x, y) };
+
+                    blend(bg.try_into().unwrap(), fg);
+                }
+            }
+        }
+    }
+}
+
+pub fn blend(bg: &mut [u8; 4], fg: [u8; 4]) {
+    if fg[3] == 0 {
+        return;
+    }
+    if fg[3] == 255 {
+        *bg = fg;
+        return;
+    }
+    #[allow(clippy::multiple_unsafe_ops_per_block)]
+    // SAFETY: no u8 can possibly become INF / NAN
+    unsafe {
+        let max = FFloat::new(255.0);
+        let bg_a = FFloat::new(bg[3] as f32) / max;
+        let fg_a = FFloat::new(fg[3] as f32) / max;
+        let a = bg_a + fg_a - bg_a * fg_a;
+        if a == 0.0 {
+            return;
+        };
+        // could turn it into array::map
+        *bg = [
+            *(max
+                * ((((FFloat::new(fg[0] as f32) / max) * fg_a)
+                    + ((FFloat::new(bg[0] as f32) / max) * bg_a) * (FFloat::new(1.0) - fg_a))
+                    / a)) as u8,
+            *(max
+                * ((((FFloat::new(fg[1] as f32) / max) * fg_a)
+                    + ((FFloat::new(bg[1] as f32) / max) * bg_a) * (FFloat::new(1.0) - fg_a))
+                    / a)) as u8,
+            *(max
+                * ((((FFloat::new(fg[2] as f32) / max) * fg_a)
+                    + ((FFloat::new(bg[2] as f32) / max) * bg_a) * (FFloat::new(1.0) - fg_a))
+                    / a)) as u8,
+            *(max * a) as u8,
+        ]
+    }
+}