Add optional focalpoint support when cropping

Author: artnez

halfshell/image.go

@@ -27,6 +27,8 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"strconv"
+	"strings"
 )
 
 // Image contains a byte array of the image data and its MIME type.
@@ -71,6 +73,31 @@ type ImageDimensions struct {
 	Height uint64
 }
 
+// Focalpoint is an x/y pair representing the location of the image subject.
+// 0.5/0.5 is the middle.
+type Focalpoint struct {
+	X float64
+	Y float64
+}
+
+// NewFocalpoint splits the given string into a Focalpoint struct. The string
+// format should be: "X,Y". For example: "0.1,0.1".
+func NewFocalpoint(s string) (fp Focalpoint) {
+	fp = Focalpoint{0.5, 0.5}
+
+	pair := strings.Split(s, ",")
+	if len(pair) != 2 {
+		return
+	}
+
+	x, _ := strconv.ParseFloat(pair[0], 64)
+	y, _ := strconv.ParseFloat(pair[1], 64)
+
+	fp.X = x
+	fp.Y = y
+	return
+}
+
 // AspectRatio returns the image dimension's aspect ratio.
 func (d ImageDimensions) AspectRatio() float64 {
 	return float64(d.Width) / float64(d.Height)

halfshell/image_processor.go

@@ -43,6 +43,7 @@ type ImageProcessorOptions struct {
 	CropMode     string
 	BorderRadius uint64
 	BGColor      string
+	Focalpoint   Focalpoint
 }
 
 type imageProcessor struct {
@@ -111,7 +112,7 @@ func (ip *imageProcessor) scaleWand(wand *imagick.MagickWand, request *ImageProc
 	}
 
 	if request.CropMode == "fill" {
-		if err = ip.cropImage(newDimensions, request.Dimensions, wand); err != nil {
+		if err = ip.cropImage(wand, newDimensions, request.Dimensions, request.Focalpoint); err != nil {
 			ip.Logger.Warnf("ImageMagick error cropping image: %s", err)
 			return true, err
 		}
@@ -295,13 +296,18 @@ func (ip *imageProcessor) clampDimensionsToMaxima(dimensions ImageDimensions, re
 	return dimensions
 }
 
-func (ip *imageProcessor) cropImage(currentDimensions ImageDimensions, requestedDimensions ImageDimensions, wand *imagick.MagickWand) (err error) {
-	err = wand.CropImage(
-		uint(requestedDimensions.Width),
-		uint(requestedDimensions.Height),
-		int((currentDimensions.Width-requestedDimensions.Width)/2),
-		int((currentDimensions.Height-requestedDimensions.Height)/2),
-	)
+func (ip *imageProcessor) cropImage(wand *imagick.MagickWand, id ImageDimensions, rd ImageDimensions, fp Focalpoint) (err error) {
+	xo := fp.X
+	yo := fp.Y
+	xc := float64(id.Width)*xo - float64(rd.Width)*xo
+	yc := float64(id.Height)*yo - float64(rd.Height)*yo
+
+	w := uint(rd.Width)
+	h := uint(rd.Height)
+	x := int(xc)
+	y := int(yc)
+
+	err = wand.CropImage(w, h, x, y)
 	return
 }
 

halfshell/route.go

@@ -72,12 +72,14 @@ func (p *Route) SourceAndProcessorOptionsForRequest(r *http.Request) (
 	borderRadius, _ := strconv.ParseUint(r.FormValue("border_radius"), 10, 32)
 	cropMode := r.FormValue("crop_mode")
 	bgColor := r.FormValue("bg_color")
+	focalpoint := r.FormValue("focalpoint")
 
 	return &ImageSourceOptions{Path: path}, &ImageProcessorOptions{
 		Dimensions:   ImageDimensions{width, height},
 		BlurRadius:   blurRadius,
 		BorderRadius: borderRadius,
 		CropMode:     cropMode,
 		BGColor:      bgColor,
+		Focalpoint:   NewFocalpoint(focalpoint),
 	}
 }