Add option to keep metadata/tags in output image (#329)

* add env var to disable stripping metadata

by default, all metadata will be stripped (as before)

* always strip orientation tags when rotating the image

in case IMGPROXY_STRIP_METADATA is false

* document IMGPROXY_STRIP_METADATA env var

* remove ICC profile after importing it

needed, in case metadata aren't stripped from the output image

processing_options.go

@@ -114,22 +114,23 @@ type watermarkOptions struct {
 }
 
 type processingOptions struct {
-	ResizingType resizeType
-	Width        int
-	Height       int
-	Dpr          float64
-	Gravity      gravityOptions
-	Enlarge      bool
-	Extend       extendOptions
-	Crop         cropOptions
-	Trim         trimOptions
-	Format       imageType
-	Quality      int
-	MaxBytes     int
-	Flatten      bool
-	Background   rgbColor
-	Blur         float32
-	Sharpen      float32
+	ResizingType  resizeType
+	Width         int
+	Height        int
+	Dpr           float64
+	Gravity       gravityOptions
+	Enlarge       bool
+	Extend        extendOptions
+	Crop          cropOptions
+	Trim          trimOptions
+	Format        imageType
+	Quality       int
+	StripMetadata bool
+	MaxBytes      int
+	Flatten       bool
+	Background    rgbColor
+	Blur          float32
+	Sharpen       float32
 
 	CacheBuster string
 
@@ -198,21 +199,22 @@ var (
 func newProcessingOptions() *processingOptions {
 	newProcessingOptionsOnce.Do(func() {
 		_newProcessingOptions = processingOptions{
-			ResizingType: resizeFit,
-			Width:        0,
-			Height:       0,
-			Gravity:      gravityOptions{Type: gravityCenter},
-			Enlarge:      false,
-			Extend:       extendOptions{Enabled: false, Gravity: gravityOptions{Type: gravityCenter}},
-			Trim:         trimOptions{Enabled: false, Threshold: 10},
-			Quality:      conf.Quality,
-			MaxBytes:     0,
-			Format:       imageTypeUnknown,
-			Background:   rgbColor{255, 255, 255},
-			Blur:         0,
-			Sharpen:      0,
-			Dpr:          1,
-			Watermark:    watermarkOptions{Opacity: 1, Replicate: false, Gravity: gravityOptions{Type: gravityCenter}},
+			ResizingType:  resizeFit,
+			Width:         0,
+			Height:        0,
+			Gravity:       gravityOptions{Type: gravityCenter},
+			Enlarge:       false,
+			Extend:        extendOptions{Enabled: false, Gravity: gravityOptions{Type: gravityCenter}},
+			Trim:          trimOptions{Enabled: false, Threshold: 10},
+			Quality:       conf.Quality,
+			StripMetadata: conf.StripMetadata,
+			MaxBytes:      0,
+			Format:        imageTypeUnknown,
+			Background:    rgbColor{255, 255, 255},
+			Blur:          0,
+			Sharpen:       0,
+			Dpr:           1,
+			Watermark:     watermarkOptions{Opacity: 1, Replicate: false, Gravity: gravityOptions{Type: gravityCenter}},
 		}
 	})