Improve handling of non-square avatars (#7025)

* Crop avatar before resizing (#1268)

Signed-off-by: Rob Watson <rfwatson@users.noreply.github.com>

* Fix spelling error

Signed-off-by: Rob Watson <rfwatson@users.noreply.github.com>

vendor/github.com/oliamb/cutter/cutter.go

@@ -0,0 +1,192 @@
+/*
+Package cutter provides a function to crop image.
+
+By default, the original image will be cropped at the
+given size from the top left corner.
+
+		croppedImg, err := cutter.Crop(img, cutter.Config{
+		  Width:  250,
+		  Height: 500,
+		})
+
+Most of the time, the cropped image will share some memory
+with the original, so it should be used read only. You must
+ask explicitely for a copy if nedded.
+
+    croppedImg, err := cutter.Crop(img, cutter.Config{
+      Width:  250,
+      Height: 500,
+      Options: Copy,
+    })
+
+It is possible to specify the top left position:
+
+		croppedImg, err := cutter.Crop(img, cutter.Config{
+		  Width:  250,
+		  Height: 500,
+		  Anchor: image.Point{100, 100},
+		  Mode:   TopLeft, // optional, default value
+		})
+
+The Anchor property can represents the center of the cropped image
+instead of the top left corner:
+
+
+		croppedImg, err := cutter.Crop(img, cutter.Config{
+		  Width: 250,
+		  Height: 500,
+		  Mode: Centered,
+		})
+
+The default crop use the specified dimension, but it is possible
+to use Width and Heigth as a ratio instead. In this case,
+the resulting image will be as big as possible to fit the asked ratio
+from the anchor position.
+
+		croppedImg, err := cutter.Crop(baseImage, cutter.Config{
+		  Width: 4,
+		  Height: 3,
+		  Mode: Centered,
+		  Options: Ratio,
+		})
+*/
+package cutter
+
+import (
+	"image"
+	"image/draw"
+)
+
+// Config is used to defined
+// the way the crop should be realized.
+type Config struct {
+	Width, Height int
+	Anchor        image.Point // The Anchor Point in the source image
+	Mode          AnchorMode  // Which point in the resulting image the Anchor Point is referring to
+	Options       Option
+}
+
+// AnchorMode is an enumeration of the position an anchor can represent.
+type AnchorMode int
+
+const (
+	// TopLeft defines the Anchor Point
+	// as the top left of the cropped picture.
+	TopLeft AnchorMode = iota
+	// Centered defines the Anchor Point
+	// as the center of the cropped picture.
+	Centered = iota
+)
+
+// Option flags to modify the way the crop is done.
+type Option int
+
+const (
+	// Ratio flag is use when Width and Height
+	// must be used to compute a ratio rather
+	// than absolute size in pixels.
+	Ratio Option = 1 << iota
+	// Copy flag is used to enforce the function
+	// to retrieve a copy of the selected pixels.
+	// This disable the use of SubImage method
+	// to compute the result.
+	Copy = 1 << iota
+)
+
+// An interface that is
+// image.Image + SubImage method.
+type subImageSupported interface {
+	SubImage(r image.Rectangle) image.Image
+}
+
+// Crop retrieves an image that is a
+// cropped copy of the original img.
+//
+// The crop is made given the informations provided in config.
+func Crop(img image.Image, c Config) (image.Image, error) {
+	maxBounds := c.maxBounds(img.Bounds())
+	size := c.computeSize(maxBounds, image.Point{c.Width, c.Height})
+	cr := c.computedCropArea(img.Bounds(), size)
+	cr = img.Bounds().Intersect(cr)
+
+	if c.Options&Copy == Copy {
+		return cropWithCopy(img, cr)
+	}
+	if dImg, ok := img.(subImageSupported); ok {
+		return dImg.SubImage(cr), nil
+	}
+	return cropWithCopy(img, cr)
+}
+
+func cropWithCopy(img image.Image, cr image.Rectangle) (image.Image, error) {
+	result := image.NewRGBA(cr)
+	draw.Draw(result, cr, img, cr.Min, draw.Src)
+	return result, nil
+}
+
+func (c Config) maxBounds(bounds image.Rectangle) (r image.Rectangle) {
+	if c.Mode == Centered {
+		anchor := c.centeredMin(bounds)
+		w := min(anchor.X-bounds.Min.X, bounds.Max.X-anchor.X)
+		h := min(anchor.Y-bounds.Min.Y, bounds.Max.Y-anchor.Y)
+		r = image.Rect(anchor.X-w, anchor.Y-h, anchor.X+w, anchor.Y+h)
+	} else {
+		r = image.Rect(c.Anchor.X, c.Anchor.Y, bounds.Max.X, bounds.Max.Y)
+	}
+	return
+}
+
+// computeSize retrieve the effective size of the cropped image.
+// It is defined by Height, Width, and Ratio option.
+func (c Config) computeSize(bounds image.Rectangle, ratio image.Point) (p image.Point) {
+	if c.Options&Ratio == Ratio {
+		// Ratio option is on, so we take the biggest size available that fit the given ratio.
+		if float64(ratio.X)/float64(bounds.Dx()) > float64(ratio.Y)/float64(bounds.Dy()) {
+			p = image.Point{bounds.Dx(), (bounds.Dx() / ratio.X) * ratio.Y}
+		} else {
+			p = image.Point{(bounds.Dy() / ratio.Y) * ratio.X, bounds.Dy()}
+		}
+	} else {
+		p = image.Point{ratio.X, ratio.Y}
+	}
+	return
+}
+
+// computedCropArea retrieve the theorical crop area.
+// It is defined by Height, Width, Mode and
+func (c Config) computedCropArea(bounds image.Rectangle, size image.Point) (r image.Rectangle) {
+	min := bounds.Min
+	switch c.Mode {
+	case Centered:
+		rMin := c.centeredMin(bounds)
+		r = image.Rect(rMin.X-size.X/2, rMin.Y-size.Y/2, rMin.X-size.X/2+size.X, rMin.Y-size.Y/2+size.Y)
+	default: // TopLeft
+		rMin := image.Point{min.X + c.Anchor.X, min.Y + c.Anchor.Y}
+		r = image.Rect(rMin.X, rMin.Y, rMin.X+size.X, rMin.Y+size.Y)
+	}
+	return
+}
+
+func (c *Config) centeredMin(bounds image.Rectangle) (rMin image.Point) {
+	if c.Anchor.X == 0 && c.Anchor.Y == 0 {
+		rMin = image.Point{
+			X: bounds.Dx() / 2,
+			Y: bounds.Dy() / 2,
+		}
+	} else {
+		rMin = image.Point{
+			X: c.Anchor.X,
+			Y: c.Anchor.Y,
+		}
+	}
+	return
+}
+
+func min(a, b int) (r int) {
+	if a < b {
+		r = a
+	} else {
+		r = b
+	}
+	return
+}