Add get_image_property() to retrieve properties

cargo test passes

CHANGELOG.md

@@ -3,6 +3,10 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [0.3.0] - 2016-01-02
+### Changed
+- Add `get_image_property()` function to retrieve, for example, EXIF data.
+
 ## [0.2.3] - 2015-12-26
 ### Changed
 - Upgrade to libc 0.2.4 in hopes of fixing downstream build incompatibilities.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "magick_rust"
-version = "0.2.3"
+version = "0.3.0"
 authors = ["Nathan Fiedler <nathanfiedler@fastmail.fm>"]
 description = "Selection of Rust bindings for the ImageMagick library."
 homepage = "https://github.com/nlfiedler/magick-rust"

README.md

@@ -1,16 +1,6 @@
 # magick-rust
 
-A "safe" Rust interface to the [ImageMagick](http://www.imagemagick.org/) system, in particular, the MagickWand library. The word *safe* is in scarequotes because, honestly, nearly everything is little more than a call into a C function with `unsafe` wrapped around it.
-
-## TODO
-
-1. ~~Use rust-bindgen to generate Rust bindings.~~
-1. ~~Add a license and copyright headers~~
-1. Develop Rustic wrappers to the MagickWand library.
-    * Old Rust bindings: https://github.com/influenza/wand-of-rust
-    * Wand API: http://www.imagemagick.org/script/magick-wand.php
-1. ~~Write unit tests~~
-1. Test it on lots of images in batches to stress test it; should not crash
+A somewhat safe Rust interface to the [ImageMagick](http://www.imagemagick.org/) system, in particular, the MagickWand library. Many of the functions in the MagickWand API are still missing, and those that are needed will be gradually added.
 
 ## Build and Test
 

src/lib.rs

@@ -31,7 +31,7 @@
 
 extern crate libc;
 
-use std::ffi::CString;
+use std::ffi::{CStr, CString};
 use std::ptr;
 use libc::{c_uint, c_double, c_void};
 use filters::FilterType;
@@ -98,6 +98,27 @@ impl MagickWand {
         }
     }
 
+    /// Retrieve the named image property value.
+    pub fn get_image_property(&self, name: &str) -> Result<&str, &'static str> {
+        let c_name = CString::new(name).unwrap();
+        let result = unsafe {
+            bindings::MagickGetImageProperty(self.wand, c_name.as_ptr())
+        };
+        let value = if result.is_null() {
+            Err("missing property")
+        } else {
+            let cstr = unsafe { CStr::from_ptr(result) };
+            match cstr.to_str() {
+                Ok(v) => Ok(v),
+                Err(_) => Err("invalid value")
+            }
+        };
+        unsafe {
+            bindings::MagickRelinquishMemory(result as *mut c_void);
+        }
+        value
+    }
+
     /// Resize the image to the specified width and height, using the
     /// specified filter type with the specified blur / sharpness factor.
     ///

tests/lib.rs

@@ -111,3 +111,20 @@ fn test_fit() {
     assert_eq!(240, wand.get_image_width());
     assert_eq!(180, wand.get_image_height());
 }
+
+#[test]
+fn test_get_image_property() {
+    START.call_once(|| {
+        magick_wand_genesis();
+    });
+    let wand = MagickWand::new();
+    assert!(wand.read_image("tests/data/IMG_5745.JPG").is_ok());
+    // retrieve a property we know exists
+    let found_value = wand.get_image_property("exif:DateTime");
+    assert!(found_value.is_ok());
+    assert_eq!("2014:04:23 13:33:08", found_value.unwrap());
+    // retrieve a property that does not exist
+    let missing_value = wand.get_image_property("exif:Foobar");
+    assert!(missing_value.is_err());
+    assert_eq!("missing property", missing_value.unwrap_err());
+}