feat(core): when building thumbnails, fallback to JPG if the source is not a browser-friendly format

If the source is browser-friendly (jpg, jpeg, png) then keep the exact original extension.

src/model/output.js

@@ -2,6 +2,8 @@ const warn = require('debug')('thumbsup:warn')
 const path = require('path')
 const urljoin = require('url-join')
 
+const BROWSER_SUPPORTED_EXT = /\.(jpg|jpeg|png)$/i
+
 exports.paths = function (filepath, mediaType, opts) {
   if (mediaType === 'image') {
     const items = imageOutput(filepath)
@@ -18,6 +20,10 @@ exports.paths = function (filepath, mediaType, opts) {
 }
 
 function imageOutput (filepath) {
+  const extension = path.extname(filepath)
+  if (!extension.match(BROWSER_SUPPORTED_EXT)) {
+    filepath = ext(filepath, 'jpg')
+  }
   return {
     thumbnail: {
       path: 'media/thumbs/' + filepath,

test/model/output.spec.js

@@ -59,6 +59,21 @@ describe('Output paths', function () {
         rel: 'fs:link'
       })
     })
+
+    it('keeps the original image format if the browser supports it', function () {
+      ['jpg', 'JPG', 'jpeg', 'JPEG', 'png', 'PNG'].forEach(ext => {
+        var o = output.paths(`holidays/beach.${ext}`, 'image', {})
+        should(o.thumbnail.path).eql(`media/thumbs/holidays/beach.${ext}`)
+      })
+    })
+
+    it('converts images to JPEG if not supported', function () {
+      // some of these formats are supported on certain browser, but we aim for maximum compatibility
+      ['bmp', 'tiff', 'webp'].forEach(ext => {
+        var o = output.paths(`holidays/beach.${ext}`, 'image', {})
+        should(o.thumbnail.path).eql(`media/thumbs/holidays/beach.jpg`)
+      })
+    })
   })
 
   describe('Videos', function () {