Auto-Orient

README.md

@@ -216,6 +216,14 @@ For Gaussian blur, the radius used is this value * the image width. This allows
 you to use a blur parameter (from 0-1) which will apply the same proportion of
 blurring to each image size.
 
+##### auto_orient
+
+If set to true, the image processor will respect EXIF rotation data. A common
+case are photos taken with a camera (eg: iPhone, digital camera) in landscape
+mode. The built-in gyroscope will embed rotation data in the image via EXIF.
+
+Disabled by default.
+
 ### Routes
 
 The `routes` block is a mapping of route patterns to route configuration values.

halfshell/config.go

@@ -73,6 +73,7 @@ type ProcessorConfig struct {
 	DefaultImageWidth       uint64
 	MaxImageDimensions      ImageDimensions
 	MaxBlurRadiusPercentage float64
+	AutoOrient              bool
 
 	// DEPRECATED
 	MaintainAspectRatio bool
@@ -228,6 +229,7 @@ func (c *configParser) parseProcessorConfig(processorName string) *ProcessorConf
 		DefaultImageWidth:       c.uintForKeypath("processors.%s.default_image_width", processorName),
 		MaxImageDimensions:      maxDimensions,
 		MaxBlurRadiusPercentage: c.floatForKeypath("processors.%s.max_blur_radius_percentage", processorName),
+		AutoOrient:              c.boolForKeypath("processors.%s.auto_orient", processorName),
 
 		// DEPRECATED
 		MaintainAspectRatio: c.boolForKeypath("processors.%s.maintain_aspect_ratio", processorName),

halfshell/image_processor.go

@@ -68,7 +68,15 @@ func (ip *imageProcessor) ProcessImage(img *Image, req *ImageProcessorOptions) e
 		req.Dimensions.Height = uint(ip.Config.DefaultImageHeight)
 	}
 
-	err := ip.resize(img, req)
+	var err error
+
+	err = ip.orient(img, req)
+	if err != nil {
+		ip.Logger.Errorf("Error orienting image: %s", err)
+		return err
+	}
+
+	err = ip.resize(img, req)
 	if err != nil {
 		ip.Logger.Errorf("Error resizing image: %s", err)
 		return err
@@ -83,6 +91,49 @@ func (ip *imageProcessor) ProcessImage(img *Image, req *ImageProcessorOptions) e
 	return nil
 }
 
+func (ip *imageProcessor) orient(img *Image, req *ImageProcessorOptions) error {
+	if !ip.Config.AutoOrient {
+		return nil
+	}
+
+	orientation := img.Wand.GetImageOrientation()
+
+	switch orientation {
+	case imagick.ORIENTATION_UNDEFINED:
+	case imagick.ORIENTATION_TOP_LEFT:
+		return nil
+	}
+
+	transparent := imagick.NewPixelWand()
+	defer transparent.Destroy()
+	transparent.SetColor("none")
+
+	var err error
+
+	switch orientation {
+	case imagick.ORIENTATION_TOP_RIGHT:
+		err = img.Wand.FlopImage()
+	case imagick.ORIENTATION_BOTTOM_RIGHT:
+		err = img.Wand.RotateImage(transparent, 180)
+	case imagick.ORIENTATION_BOTTOM_LEFT:
+		err = img.Wand.FlipImage()
+	case imagick.ORIENTATION_LEFT_TOP:
+		err = img.Wand.TransposeImage()
+	case imagick.ORIENTATION_RIGHT_TOP:
+		err = img.Wand.RotateImage(transparent, 90)
+	case imagick.ORIENTATION_RIGHT_BOTTOM:
+		err = img.Wand.TransverseImage()
+	case imagick.ORIENTATION_LEFT_BOTTOM:
+		err = img.Wand.RotateImage(transparent, 270)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	return img.Wand.SetImageOrientation(imagick.ORIENTATION_TOP_LEFT)
+}
+
 func (ip *imageProcessor) resize(img *Image, req *ImageProcessorOptions) error {
 	scaleMode := req.ScaleMode
 	if scaleMode == 0 {