Add image.Exif

Note that we will probably need to add some metadata cache for this to scale.

Fixes #4600

resources/images/config.go

@@ -119,6 +119,11 @@ func DecodeConfig(m map[string]interface{}) (Imaging, error) {
 		i.ResampleFilter = filter
 	}
 
+	if strings.TrimSpace(i.Exif.IncludeFields) == "" && strings.TrimSpace(i.Exif.ExcludeFields) == "" {
+		// Don't change this for no good reason. Please don't.
+		i.Exif.ExcludeFields = "GPS|Exif|Exposure[M|P|B]|Contrast|Resolution|Sharp|JPEG|Metering|Sensing|Saturation|ColorSpace|Flash|WhiteBalance"
+	}
+
 	return i, nil
 }
 
@@ -279,4 +284,29 @@ type Imaging struct {
 
 	// The anchor to use in Fill. Default is "smart", i.e. Smart Crop.
 	Anchor string
+
+	Exif ExifConfig
+}
+
+type ExifConfig struct {
+
+	// Regexp matching the Exif fields you want from the (massive) set of Exif info
+	// available. As we cache this info to disk, this is for performance and
+	// disk space reasons more than anything.
+	// If you want it all, put ".*" in this config setting.
+	// Note that if neither this or ExcludeFields is set, Hugo will return a small
+	// default set.
+	IncludeFields string
+
+	// Regexp matching the Exif fields you want to exclude. This may be easier to use
+	// than IncludeFields above, depending on what you want.
+	ExcludeFields string
+
+	// Hugo extracts the "photo taken" date/time into .Date by default.
+	// Set this to true to turn it off.
+	DisableDate bool
+
+	// Hugo extracts the "photo taken where" (GPS latitude and longitude) into
+	// .Long and .Lat. Set this to true to turn it off.
+	DisableLatLong bool
 }