Only shrink when resizing with fit (#803)

components/imageproc/src/lib.rs

@@ -41,8 +41,8 @@ pub enum ResizeOp {
     /// Scales the image to a specified height with width computed such
     /// that aspect ratio is preserved
     FitHeight(u32),
-    /// Scales the image such that it fits within the specified width and
+    /// If the image is larger than the specified width or height, scales the image such
-    /// height preserving aspect ratio.
+    /// that it fits within the specified width and height preserving aspect ratio.
     /// Either dimension may end up being smaller, but never larger than specified.
     Fit(u32, u32),
     /// Scales the image such that it fills the specified width and height.
@@ -266,7 +266,13 @@ impl ImageOp {
             Scale(w, h) => img.resize_exact(w, h, RESIZE_FILTER),
             FitWidth(w) => img.resize(w, u32::max_value(), RESIZE_FILTER),
             FitHeight(h) => img.resize(u32::max_value(), h, RESIZE_FILTER),
-            Fit(w, h) => img.resize(w, h, RESIZE_FILTER),
+            Fit(w, h) => {
+                if img_w > w || img_h > h {
+                    img.resize(w, h, RESIZE_FILTER)
+                } else {
+                    img
+                }
+            },
             Fill(w, h) => {
                 let factor_w = img_w as f32 / w as f32;
                 let factor_h = img_h as f32 / h as f32;

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

@@ -78,10 +78,16 @@ The source for all examples is this 300 × 380 pixels image:
   {{ resize_image(path="documentation/content/image-processing/01-zola.png", width=0, height=150, op="fit_height") }}
 
 ### **`"fit"`**
-  Like `"fit_width"` and `"fit_height"` combined.
+  Like `"fit_width"` and `"fit_height"` combined, but only resize if the image is bigger than any of the specified dimensions.
+  This mode is handy, if e.g. images are automatically shrinked to certain sizes in a shortcode for mobile optimization.
   Resizes the image such that the result fits within `width` and `height` preserving aspect ratio. This means that both width or height
   will be at max `width` and `height`, respectively, but possibly one of them smaller so as to preserve the aspect ratio.
 
+
+  `resize_image(..., width=5000, height=5000, op="fit")`
+
+  {{ resize_image(path="documentation/content/image-processing/01-zola.png", width=5000, height=5000, op="fit") }}
+
   `resize_image(..., width=150, height=150, op="fit")`
 
   {{ resize_image(path="documentation/content/image-processing/01-zola.png", width=150, height=150, op="fit") }}