Implements #421 processing option to control meta stripping (#422)

* Implements processing option to control meta stripping

* Update based on code review comments

Change name of option to "stripmeta" and change how we handle config vs request setting logic

* Fix indentation style typo

* Fix indentation style typo

* Use full metadata naming for config and variables

Co-authored-by: John Koehl <johnk@zillowgroup.com>
Co-authored-by: John Koehl <jkoehl>

docs/generating_the_url_advanced.md

@@ -428,6 +428,17 @@ It's highly recommended to prefer `cachebuster` option over URL query string bec
 
 Default: empty
 
+#### Strip Metadata
+
+```
+strip_metadata:%strip_metadata
+sm:%strip_metadata
+```
+
+When set to `1`, `t` or `true`, imgproxy will strip the metadata (EXIF, IPTC, etc.) on JPEG and WebP output images. Normally this is controlled by the [IMGPROXY_STRIP_METADATA](configuration.md#miscellaneous) configuration but this procesing option allows the configuration to be set for each request.
+
+Default: `false`
+
 #### Filename
 
 ```

process.go

@@ -639,7 +639,7 @@ func saveImageToFitBytes(po *processingOptions, img *vipsImage) ([]byte, context
 	img.CopyMemory()
 
 	for {
-		result, cancel, err := img.Save(po.Format, quality, conf.StripMetadata)
+		result, cancel, err := img.Save(po.Format, quality, po.StripMetadata)
 		if len(result) <= po.MaxBytes || quality <= 10 || err != nil {
 			return result, cancel, err
 		}
@@ -767,5 +767,5 @@ func processImage(ctx context.Context) ([]byte, context.CancelFunc, error) {
 		return saveImageToFitBytes(po, img)
 	}
 
-	return img.Save(po.Format, po.Quality, conf.StripMetadata)
+	return img.Save(po.Format, po.Quality, po.StripMetadata)
 }

processing_options.go

@@ -143,6 +143,7 @@ type processingOptions struct {
 	Background    rgbColor
 	Blur          float32
 	Sharpen       float32
+	StripMetadata bool
 
 	CacheBuster string
 
@@ -227,6 +228,7 @@ func newProcessingOptions() *processingOptions {
 			Sharpen:       0,
 			Dpr:           1,
 			Watermark:     watermarkOptions{Opacity: 1, Replicate: false, Gravity: gravityOptions{Type: gravityCenter}},
+			StripMetadata: conf.StripMetadata,
 		}
 	})
 
@@ -848,6 +850,14 @@ func applyFilenameOption(po *processingOptions, args []string) error {
 	return nil
 }
 
+func applyMetaStripmetaOption(po *processingOptions, args []string) error {
+	if len(args[0]) > 0 {
+		po.StripMetadata = parseBoolOption(args[0])
+	}
+
+	return nil
+}
+
 func applyProcessingOption(po *processingOptions, name string, args []string) error {
 	switch name {
 	case "format", "f", "ext":
@@ -894,6 +904,8 @@ func applyProcessingOption(po *processingOptions, name string, args []string) er
 		return applyCacheBusterOption(po, args)
 	case "filename", "fn":
 		return applyFilenameOption(po, args)
+	case "strip_metadata", "sm":
+		return applyMetaStripmetaOption(po, args)
 	}
 
 	return fmt.Errorf("Unknown processing option: %s", name)

processing_options_test.go

@@ -405,6 +405,16 @@ func (s *ProcessingOptionsTestSuite) TestParsePathAdvancedCachebuster() {
 	assert.Equal(s.T(), "123", po.CacheBuster)
 }
 
+func (s *ProcessingOptionsTestSuite) TestParsePathAdvancedStripMetadata() {
+	req := s.getRequest("http://example.com/unsafe/strip_metadata:true/plain/http://images.dev/lorem/ipsum.jpg")
+	ctx, err := parsePath(context.Background(), req)
+
+	require.Nil(s.T(), err)
+
+	po := getProcessingOptions(ctx)
+	assert.True(s.T(), po.StripMetadata)
+}
+
 func (s *ProcessingOptionsTestSuite) TestParsePathWebpDetection() {
 	conf.EnableWebpDetection = true