Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/image/src/math/utils.rs

@@ -0,0 +1,123 @@
+//! Shared mathematical utility functions.
+
+use std::cmp::max;
+
+/// Calculates the width and height an image should be resized to.
+/// This preserves aspect ratio, and based on the `fill` parameter
+/// will either fill the dimensions to fit inside the smaller constraint
+/// (will overflow the specified bounds on one axis to preserve
+/// aspect ratio), or will shrink so that both dimensions are
+/// completely contained within the given `width` and `height`,
+/// with empty space on one axis.
+pub(crate) fn resize_dimensions(
+    width: u32,
+    height: u32,
+    nwidth: u32,
+    nheight: u32,
+    fill: bool,
+) -> (u32, u32) {
+    let wratio = nwidth as f64 / width as f64;
+    let hratio = nheight as f64 / height as f64;
+
+    let ratio = if fill {
+        f64::max(wratio, hratio)
+    } else {
+        f64::min(wratio, hratio)
+    };
+
+    let nw = max((width as f64 * ratio).round() as u64, 1);
+    let nh = max((height as f64 * ratio).round() as u64, 1);
+
+    if nw > u64::from(u32::MAX) {
+        let ratio = u32::MAX as f64 / width as f64;
+        (u32::MAX, max((height as f64 * ratio).round() as u32, 1))
+    } else if nh > u64::from(u32::MAX) {
+        let ratio = u32::MAX as f64 / height as f64;
+        (max((width as f64 * ratio).round() as u32, 1), u32::MAX)
+    } else {
+        (nw as u32, nh as u32)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    quickcheck! {
+        fn resize_bounds_correctly_width(old_w: u32, new_w: u32) -> bool {
+            if old_w == 0 || new_w == 0 { return true; }
+            // In this case, the scaling is limited by scaling of height.
+            // We could check that case separately but it does not conform to the same expectation.
+            if new_w as u64 * 400u64 >= old_w as u64 * u64::from(u32::MAX) { return true; }
+
+            let result = super::resize_dimensions(old_w, 400, new_w, ::std::u32::MAX, false);
+            let exact = (400 as f64 * new_w as f64 / old_w as f64).round() as u32;
+            result.0 == new_w && result.1 == exact.max(1)
+        }
+    }
+
+    quickcheck! {
+        fn resize_bounds_correctly_height(old_h: u32, new_h: u32) -> bool {
+            if old_h == 0 || new_h == 0 { return true; }
+            // In this case, the scaling is limited by scaling of width.
+            // We could check that case separately but it does not conform to the same expectation.
+            if 400u64 * new_h as u64 >= old_h as u64 * u64::from(u32::MAX) { return true; }
+
+            let result = super::resize_dimensions(400, old_h, ::std::u32::MAX, new_h, false);
+            let exact = (400 as f64 * new_h as f64 / old_h as f64).round() as u32;
+            result.1 == new_h && result.0 == exact.max(1)
+        }
+    }
+
+    #[test]
+    fn resize_handles_fill() {
+        let result = super::resize_dimensions(100, 200, 200, 500, true);
+        assert!(result.0 == 250);
+        assert!(result.1 == 500);
+
+        let result = super::resize_dimensions(200, 100, 500, 200, true);
+        assert!(result.0 == 500);
+        assert!(result.1 == 250);
+    }
+
+    #[test]
+    fn resize_never_rounds_to_zero() {
+        let result = super::resize_dimensions(1, 150, 128, 128, false);
+        assert!(result.0 > 0);
+        assert!(result.1 > 0);
+    }
+
+    #[test]
+    fn resize_handles_overflow() {
+        let result = super::resize_dimensions(100, ::std::u32::MAX, 200, ::std::u32::MAX, true);
+        assert!(result.0 == 100);
+        assert!(result.1 == ::std::u32::MAX);
+
+        let result = super::resize_dimensions(::std::u32::MAX, 100, ::std::u32::MAX, 200, true);
+        assert!(result.0 == ::std::u32::MAX);
+        assert!(result.1 == 100);
+    }
+
+    #[test]
+    fn resize_rounds() {
+        // Only truncation will result in (3840, 2229) and (2160, 3719)
+        let result = super::resize_dimensions(4264, 2476, 3840, 2160, true);
+        assert_eq!(result, (3840, 2230));
+
+        let result = super::resize_dimensions(2476, 4264, 2160, 3840, false);
+        assert_eq!(result, (2160, 3720));
+    }
+
+    #[test]
+    fn resize_handles_zero() {
+        let result = super::resize_dimensions(0, 100, 100, 100, false);
+        assert_eq!(result, (1, 100));
+
+        let result = super::resize_dimensions(100, 0, 100, 100, false);
+        assert_eq!(result, (100, 1));
+
+        let result = super::resize_dimensions(100, 100, 0, 100, false);
+        assert_eq!(result, (1, 1));
+
+        let result = super::resize_dimensions(100, 100, 100, 0, false);
+        assert_eq!(result, (1, 1));
+    }
+}