Fix for #632 - add ability to get asset image dimensions (#670)

Cargo.lock

@@ -2364,6 +2364,7 @@ dependencies = [
  "config 0.1.0",
  "csv 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "errors 0.1.0",
+ "image 0.21.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "imageproc 0.1.0",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "library 0.1.0",

components/site/src/lib.rs

@@ -395,6 +395,10 @@ impl Site {
             "resize_image",
             global_fns::ResizeImage::new(self.imageproc.clone()),
         );
+        self.tera.register_function(
+            "get_image_metadata",
+            global_fns::GetImageMeta::new(self.content_path.clone()),
+        );
         self.tera.register_function("load_data", global_fns::LoadData::new(self.base_path.clone()));
         self.tera.register_function("trans", global_fns::Trans::new(self.config.clone()));
         self.tera.register_function(

components/templates/Cargo.toml

@@ -10,6 +10,7 @@ lazy_static = "1"
 pulldown-cmark = "0.2"
 toml = "0.4"
 csv = "1"
+image = "0.21"
 serde_json = "1.0"
 reqwest = "0.9"
 url = "1.5"

components/templates/src/global_fns/mod.rs

@@ -2,11 +2,13 @@ use std::collections::HashMap;
 use std::path::PathBuf;
 use std::sync::{Arc, Mutex, RwLock};
 
-use tera::{from_value, to_value, Function as TeraFn, Result, Value};
+use tera::{from_value, to_value, Error, Function as TeraFn, Result, Value};
 
 use config::Config;
 use library::{Library, Taxonomy};
 use utils::site::resolve_internal_link;
+use image;
+use image::GenericImageView;
 
 use imageproc;
 
@@ -140,6 +142,39 @@ impl TeraFn for ResizeImage {
     }
 }
 
+#[derive(Debug)]
+pub struct GetImageMeta {
+    content_path: PathBuf
+}
+
+impl GetImageMeta {
+    pub fn new(content_path: PathBuf) -> Self {
+        Self { content_path }
+    }
+}
+
+impl TeraFn for GetImageMeta {
+    fn call(&self, args: &HashMap<String, Value>) -> Result<Value> {
+        let path = required_arg!(
+            String,
+            args.get("path"),
+            "`get_image_meta` requires a `path` argument with a string value"
+        );
+        let src_path = self.content_path.join(&path);
+        if !src_path.exists(){
+            return Err(format!("`get_image_meta`: Cannot find path: {}", path).into());
+        }
+        let img = image::open(&src_path)
+            .map_err(|e| Error::chain(format!("Failed to process image: {}", path), e))?;
+        let mut map = tera::Map::new();
+        map.insert(String::from("height"), Value::Number(tera::Number::from(img.height())));
+        map.insert(String::from("width"), Value::Number(tera::Number::from(img.width())));
+        Ok(Value::Object(map))
+    }
+}
+
+
+
 #[derive(Debug)]
 pub struct GetTaxonomyUrl {
     taxonomies: HashMap<String, HashMap<String, String>>,

components/templates/src/lib.rs

@@ -7,7 +7,7 @@ extern crate csv;
 extern crate pulldown_cmark;
 extern crate reqwest;
 extern crate url;
-
+extern crate image;
 #[cfg(test)]
 #[macro_use]
 extern crate serde_json;

docs/content/documentation/content/image-processing/index.md

@@ -145,3 +145,9 @@ Here is the result:
 <small>
   Image attribution: Public domain, except: _06-example.jpg_: Willi Heidelbach, _07-example.jpg_: Daniel Ullrich.
 </small>
+
+
+## Get image size
+
+Sometimes when building a gallery it is useful to know the dimensions of each asset.  You can get this information with
+[get_image_metadata](./documentation/templates/overview.md#get-image-metadata) 

docs/content/documentation/templates/overview.md

@@ -130,6 +130,14 @@ In the case of non-internal links, you can also add a cachebust of the format `?
 by passing `cachebust=true` to the `get_url` function.
 
 
+### `get_image_metadata`
+Gets metadata for an image.  Today the only supported keys are `width` and `height`.
+
+```jinja2
+  {% set meta = get_image_metadata(path="...") %}
+  Our image is {{ meta.width }}x{{ meta.height }}
+```
+
 ### `get_taxonomy_url`
 Gets the permalink for the taxonomy item found.