Allow images to be cropped without being resized

Introduces the Crop method for image processing which implements gift.CropToSize. Also allows a smartCrop without resizing, and updates the documentation.

Fixes #9499

resources/errorResource.go

@@ -100,6 +100,10 @@ func (e *errorResource) Width() int {
 	panic(e.error)
 }
 
+func (e *errorResource) Crop(spec string) (resource.Image, error) {
+	panic(e.error)
+}
+
 func (e *errorResource) Fill(spec string) (resource.Image, error) {
 	panic(e.error)
 }

resources/image.go

@@ -181,6 +181,19 @@ func (i *imageResource) Resize(spec string) (resource.Image, error) {
 	})
 }
 
+// Crop the image to the specified dimensions without resizing using the given anchor point.
+// Space delimited config: 200x300 TopLeft
+func (i *imageResource) Crop(spec string) (resource.Image, error) {
+	conf, err := i.decodeImageConfig("crop", spec)
+	if err != nil {
+		return nil, err
+	}
+
+	return i.doWithImageConfig(conf, func(src image.Image) (image.Image, error) {
+		return i.Proc.ApplyFiltersFromConfig(src, conf)
+	})
+}
+
 // Fit scales down the image using the specified resample filter to fit the specified
 // maximum width and height.
 func (i *imageResource) Fit(spec string) (resource.Image, error) {

resources/image_test.go

@@ -137,6 +137,22 @@ func TestImageTransformBasic(t *testing.T) {
 	filledAgain, err := image.Fill("200x100 bottomLeft")
 	c.Assert(err, qt.IsNil)
 	c.Assert(filled, eq, filledAgain)
+
+	cropped, err := image.Crop("300x300 topRight")
+	c.Assert(err, qt.IsNil)
+	c.Assert(cropped.RelPermalink(), qt.Equals, "/a/sunset_hu59e56ffff1bc1d8d122b1403d34e039f_90587_300x300_crop_q68_linear_topright.jpg")
+	assertWidthHeight(cropped, 300, 300)
+
+	smartcropped, err := image.Crop("200x200 smart")
+	c.Assert(err, qt.IsNil)
+	c.Assert(smartcropped.RelPermalink(), qt.Equals, fmt.Sprintf("/a/sunset_hu59e56ffff1bc1d8d122b1403d34e039f_90587_200x200_crop_q68_linear_smart%d.jpg", 1))
+	assertWidthHeight(smartcropped, 200, 200)
+
+	// Check cache
+	croppedAgain, err := image.Crop("300x300 topRight")
+	c.Assert(err, qt.IsNil)
+	c.Assert(cropped, eq, croppedAgain)
+
 }
 
 func TestImageTransformFormat(t *testing.T) {

resources/images/config.go

@@ -364,7 +364,7 @@ func (i ImageConfig) GetKey(format Format) string {
 
 	k += "_" + i.FilterStr
 
-	if strings.EqualFold(i.Action, "fill") {
+	if strings.EqualFold(i.Action, "fill") || strings.EqualFold(i.Action, "crop") {
 		k += "_" + anchor
 	}
 

resources/images/image.go

@@ -207,6 +207,21 @@ func (p *ImageProcessor) ApplyFiltersFromConfig(src image.Image, conf ImageConfi
 	switch conf.Action {
 	case "resize":
 		filters = append(filters, gift.Resize(conf.Width, conf.Height, conf.Filter))
+	case "crop":
+		if conf.AnchorStr == smartCropIdentifier {
+			bounds, err := p.smartCrop(src, conf.Width, conf.Height, conf.Filter)
+			if err != nil {
+				return nil, err
+			}
+
+			// First crop using the bounds returned by smartCrop.
+			filters = append(filters, gift.Crop(bounds))
+			// Then center crop the image to get an image the desired size without resizing.
+			filters = append(filters, gift.CropToSize(conf.Width, conf.Height, gift.CenterAnchor))
+
+		} else {
+			filters = append(filters, gift.CropToSize(conf.Width, conf.Height, conf.Anchor))
+		}
 	case "fill":
 		if conf.AnchorStr == smartCropIdentifier {
 			bounds, err := p.smartCrop(src, conf.Width, conf.Height, conf.Filter)

resources/resource/resourcetypes.go

@@ -62,6 +62,7 @@ type Image interface {
 type ImageOps interface {
 	Height() int
 	Width() int
+	Crop(spec string) (Image, error)
 	Fill(spec string) (Image, error)
 	Fit(spec string) (Image, error)
 	Resize(spec string) (Image, error)

resources/transform.go

@@ -176,6 +176,10 @@ func (r *resourceAdapter) Data() interface{} {
 	return r.target.Data()
 }
 
+func (r *resourceAdapter) Crop(spec string) (resource.Image, error) {
+	return r.getImageOps().Crop(spec)
+}
+
 func (r *resourceAdapter) Fill(spec string) (resource.Image, error) {
 	return r.getImageOps().Fill(spec)
 }