From c50b3e27de64efe52c549dcf13e0cb4e0143469c Mon Sep 17 00:00:00 2001
From: gentoo90 <gentoo90@gmail.com>
Date: Tue, 16 May 2017 16:43:08 +0300
Subject: [PATCH] Add `compare_images` method

---
 src/lib.rs         |  1 +
 src/wand/magick.rs | 16 ++++++++++++++++
 tests/lib.rs       | 19 ++++++++++++++++++-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 49974ff..2f8514d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -37,6 +37,7 @@ mod conversions;
 include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
 
 pub use wand::*;
+pub use bindings::MetricType;
 
 use libc::size_t;
 #[cfg(not(target_os = "freebsd"))]
diff --git a/src/wand/magick.rs b/src/wand/magick.rs
index aed6612..a7a5a87 100644
--- a/src/wand/magick.rs
+++ b/src/wand/magick.rs
@@ -122,6 +122,22 @@ impl MagickWand {
         }
     }
 
+    /// Compare two images and return tuple `(distortion, diffImage)`
+    /// `diffImage` is `None` if `distortion == 0`
+    pub fn compare_images(&self, reference: &MagickWand, metric: bindings::MetricType) -> (f64, Option<MagickWand>) {
+        let mut distortion: f64 = 0.0;
+        let result = unsafe {
+            bindings::MagickCompareImages(self.wand, reference.wand, metric, &mut distortion)
+        };
+        let wand = if result.is_null() {
+            None
+        }
+        else {
+            Some(MagickWand { wand: result })
+        };
+        (distortion, wand)
+    }
+
     /// Retrieve the width of the image.
     pub fn get_image_width(&self) -> usize {
         unsafe {
diff --git a/tests/lib.rs b/tests/lib.rs
index 99de8a7..3f37d6f 100644
--- a/tests/lib.rs
+++ b/tests/lib.rs
@@ -16,7 +16,7 @@
 
 extern crate magick_rust;
 
-use magick_rust::{MagickWand, magick_wand_genesis};
+use magick_rust::{MagickWand, magick_wand_genesis, MetricType};
 
 use std::error::Error;
 use std::fs::File;
@@ -177,6 +177,23 @@ fn test_auto_orient() {
     assert_eq!(false, wand.requires_orientation());
 }
 
+#[test]
+fn test_compare_images() {
+    START.call_once(|| {
+        magick_wand_genesis();
+    });
+    let wand1 = MagickWand::new();
+    assert!(wand1.read_image("tests/data/IMG_5745.JPG").is_ok());
+
+    let wand2 = MagickWand::new();
+    assert!(wand2.read_image("tests/data/IMG_5745_rotl.JPG").is_ok());
+    wand2.auto_orient();
+
+    let (distortion, diff) = wand1.compare_images(&wand2, MetricType::RootMeanSquaredErrorMetric);
+    assert!(distortion < 0.01);
+    assert!(diff.is_some());
+}
+
 #[test]
 fn test_set_option() {
     START.call_once(|| {