fix text_size (#689)

src/drawing/text.rs

@@ -13,32 +13,36 @@ fn layout_glyphs(
     text: &str,
     mut f: impl FnMut(OutlinedGlyph, Rect),
 ) -> (u32, u32) {
-    let (mut w, mut h) = (0f32, 0f32);
-
+    if text.is_empty() {
+        return (0, 0);
+    }
     let font = font.as_scaled(scale);
-    let mut last: Option<GlyphId> = None;
+
+    let mut w = 0.0;
+    let mut prev: Option<GlyphId> = None;
 
     for c in text.chars() {
         let glyph_id = font.glyph_id(c);
         let glyph = glyph_id.with_scale_and_position(scale, point(w, font.ascent()));
         w += font.h_advance(glyph_id);
         if let Some(g) = font.outline_glyph(glyph) {
-            if let Some(last) = last {
-                w += font.kern(glyph_id, last);
+            if let Some(prev) = prev {
+                w += font.kern(glyph_id, prev);
             }
-            last = Some(glyph_id);
+            prev = Some(glyph_id);
             let bb = g.px_bounds();
-            h = h.max(bb.height());
             f(g, bb);
         }
     }
 
-    (w as u32, h as u32)
+    let w = w.ceil();
+    let h = font.height().ceil();
+    assert!(w >= 0.0);
+    assert!(h >= 0.0);
+    (1 + w as u32, h as u32)
 }
 
 /// Get the width and height of the given text, rendered with the given font and scale.
-///
-/// Note that this function *does not* support newlines, you must do this manually.
 pub fn text_size(scale: impl Into<PxScale> + Copy, font: &impl Font, text: &str) -> (u32, u32) {
     layout_glyphs(scale, font, text, |_, _| {})
 }
@@ -67,6 +71,7 @@ where
     draw_text_mut(&mut out, color, x, y, scale, font, text);
     out
 }
+
 #[doc=generate_mut_doc_comment!("draw_text")]
 pub fn draw_text_mut<C>(
     canvas: &mut C,
@@ -84,11 +89,11 @@ pub fn draw_text_mut<C>(
     let image_height = canvas.height() as i32;
 
     layout_glyphs(scale, font, text, |g, bb| {
-        let bbx = x + bb.min.x.round() as i32;
-        let bby = y + bb.min.y.round() as i32;
+        let x_shift = x + bb.min.x.round() as i32;
+        let y_shift = y + bb.min.y.round() as i32;
         g.draw(|gx, gy, gv| {
-            let image_x = gx as i32 + bbx;
-            let image_y = gy as i32 + bby;
+            let image_x = gx as i32 + x_shift;
+            let image_y = gy as i32 + y_shift;
 
             if (0..image_width).contains(&image_x) && (0..image_height).contains(&image_y) {
                 let image_x = image_x as u32;
@@ -101,3 +106,55 @@ pub fn draw_text_mut<C>(
         })
     });
 }
+
+#[cfg(not(miri))]
+#[cfg(test)]
+mod proptests {
+    use super::*;
+    use crate::{
+        proptest_utils::arbitrary_image_with,
+        rect::{Rect, Region},
+    };
+    use ab_glyph::FontRef;
+    use image::Luma;
+    use proptest::prelude::*;
+
+    const FONT_BYTES: &[u8] = include_bytes!("../../tests/data/fonts/DejaVuSans.ttf");
+
+    proptest! {
+        #[test]
+        fn proptest_text_size(
+            img in arbitrary_image_with::<Luma<u8>>(Just(0), 0..=100, 0..=100),
+            x in 0..100,
+            y in 0..100,
+            scale in 0.0..100f32,
+            ref text in "[0-9a-zA-Z]*",
+        ) {
+            let font = FontRef::try_from_slice(FONT_BYTES).unwrap();
+            let background = Luma([0]);
+            let text_color = Luma([255u8]);
+
+            let img = draw_text(&img, text_color, x, y, scale, &font, text);
+
+            let (text_w, text_h) = text_size(scale, &font, text);
+            if text.is_empty() {
+                return Ok(());
+            }
+
+            let first_char = text.chars().next().unwrap();
+            let first_x_bearing =
+                font.as_scaled(scale).h_side_bearing(font.glyph_id(first_char));
+            let rect = if first_x_bearing < 0.0 {
+                let x_shift = first_x_bearing.abs().ceil() as i32;
+                Rect::at(x - x_shift, y).of_size(text_w + x_shift as u32, text_h)
+            } else {
+                Rect::at(x, y).of_size(text_w, text_h)
+            };
+            for (px, py, &p) in img.enumerate_pixels() {
+                if !rect.contains(px as i32, py as i32) {
+                    assert_eq!(p, background, "pixel_position: {:?}, rect: {:?}", (px, py), rect);
+                }
+            }
+        }
+    }
+}

tests/regression.rs

@@ -23,9 +23,11 @@ use image::{
 
 use imageproc::contrast::ThresholdType;
 use imageproc::definitions::Image;
+use imageproc::drawing::text_size;
 use imageproc::filter::bilateral::GaussianEuclideanColorDistance;
 use imageproc::filter::bilateral_filter;
 use imageproc::kernel::{self};
+use imageproc::rect::{Rect, Region};
 use imageproc::{
     definitions::{Clamp, HasBlack, HasWhite},
     edges::canny,
@@ -826,19 +828,23 @@ fn test_bilateral_filter() {
 
 #[test]
 fn test_draw_text() {
-    let mut image = GrayImage::from_pixel(300, 300, Luma::black());
     let font_bytes = include_bytes!("data/fonts/DejaVuSans.ttf");
     let font = ab_glyph::FontRef::try_from_slice(font_bytes).unwrap();
 
-    imageproc::drawing::draw_text_mut(
-        &mut image,
-        Luma::white(),
-        50,
-        100,
-        30.0f32,
-        &font,
-        "Hello world!",
-    );
-
-    compare_to_truth_image(&image, "text.png");
+    let background = Luma::black();
+    let mut img = GrayImage::from_pixel(300, 300, background);
+
+    let text = "Hello world!";
+    let scale = 30.0;
+    let (x, y) = (50, 100);
+    imageproc::drawing::draw_text_mut(&mut img, Luma::white(), x, y, scale, &font, text);
+    compare_to_truth_image(&img, "text.png");
+
+    let (text_w, text_h) = text_size(scale, &font, text);
+    let rect = Rect::at(x, y).of_size(text_w, text_h);
+    for (px, py, &p) in img.enumerate_pixels() {
+        if !rect.contains(px as i32, py as i32) {
+            assert_eq!(p, background);
+        }
+    }
 }