Refactored bitmap API (partially)

- Made the scale option an interface (for easier use)
- Added rotation option
- Added utility function that converts Go bitmap to an Allegro bitmap (using a temporary file)

allegro5/bitmap.go

@@ -6,6 +6,10 @@ import "C"
 
 import (
 	"fmt"
+	"image"
+	"image/png"
+	"io/ioutil"
+	"os"
 	"unsafe"
 )
 
@@ -18,13 +22,35 @@ type Bitmap struct {
 
 type DrawOptions struct {
 	Center   bool
-	Scale  *Scale
+	Scale    Scale
 	Tint     *Color
+	Rotation *Rotation
 }
 
-type Scale struct {
+type Scale interface {
-	Horizontal float32
+	Horizontal() float32
-	Vertical   float32
+	Vertical() float32
+}
+
+type scale struct {
+	horizontal float32
+	vertical   float32
+}
+
+func (s *scale) Horizontal() float32 { return s.horizontal }
+func (s *scale) Vertical() float32   { return s.vertical }
+
+func NewScale(horizontal, vertical float32) Scale {
+	return &scale{horizontal, vertical}
+}
+
+func NewUniformScale(s float32) Scale {
+	return &scale{s, s}
+}
+
+type Rotation struct {
+	Angle  float32
+	Center bool
 }
 
 // NewBitmap creates a new bitmap of given width and height
@@ -36,6 +62,29 @@ func NewBitmap(width, height int) (*Bitmap, error) {
 	return &Bitmap{b, width, height}, nil
 }
 
+func exportToPng(im image.Image) (string, error) {
+	tmp, err := ioutil.TempFile("", "galleg")
+	if nil != err {
+		return "", err
+	}
+	defer tmp.Close()
+	err = png.Encode(tmp, im)
+	if nil != err {
+		return "", err
+	}
+	return tmp.Name(), nil
+}
+
+// NewBitmapFromImage creates a new bitmap starting from a Go native image (image.Image)
+func NewBitmapFromImage(im image.Image) (*Bitmap, error) {
+	path, err := exportToPng(im)
+	if nil != err {
+		return nil, err
+	}
+	defer os.Remove(path)
+	return LoadBitmap(path)
+}
+
 // LoadBitmap tries to load the image at the specified path as a bitmap
 func LoadBitmap(path string) (*Bitmap, error) {
 	p := C.CString(path)
@@ -60,27 +109,50 @@ func (b *Bitmap) DrawOptions(left, top float32, options DrawOptions) {
 
 	scale := nil != options.Scale
 	if scale {
-		width *= options.Scale.Horizontal
+		width *= options.Scale.Horizontal()
-		height *= options.Scale.Vertical
+		height *= options.Scale.Vertical()
 	}
 	if options.Center {
 		left -= width * 0.5
 		top -= height * 0.5
 	}
+	rotated := nil != options.Rotation
+	var centerX C.float
+	var centerY C.float
+	if rotated && options.Rotation.Center {
+		centerX = C.float(b.width) * 0.5
+		centerY = C.float(b.height) * 0.5
+	}
 
 	if scale {
-		if nil == options.Tint {
+		if nil == options.Tint { // scaled
+			if rotated { // scaled & rotated
+				C.al_draw_scaled_rotated_bitmap(b.bitmap, centerX, centerY, C.float(left), C.float(top), C.float(options.Scale.Horizontal()), C.float(options.Scale.Vertical()), C.float(options.Rotation.Angle), 0)
+			} else { // scaled
 				C.al_draw_scaled_bitmap(b.bitmap, 0, 0, C.float(b.width), C.float(b.height), C.float(left), C.float(top), C.float(width), C.float(height), 0)
-		} else {
+			}
+		} else { // tinted & scaled
+			if rotated { // scaled, tinted & rotated
+				C.al_draw_tinted_scaled_rotated_bitmap(b.bitmap, options.Tint.color, centerX, centerY, C.float(left), C.float(top), C.float(options.Scale.Horizontal()), C.float(options.Scale.Vertical()), C.float(options.Rotation.Angle), 0)
+			} else { // tinted, scaled
 				C.al_draw_tinted_scaled_bitmap(b.bitmap, options.Tint.color, 0, 0, C.float(b.width), C.float(b.height), C.float(left), C.float(top), C.float(width), C.float(height), 0)
 			}
+		}
 	} else {
 		if nil == options.Tint {
+			if rotated { // rotated
+				C.al_draw_rotated_bitmap(b.bitmap, centerX, centerY, C.float(left), C.float(top), C.float(options.Rotation.Angle), 0)
+			} else {
 				C.al_draw_bitmap(b.bitmap, C.float(left), C.float(top), 0)
+			}
+		} else { // tinted
+			if rotated { // tinted & rotated
+				C.al_draw_tinted_rotated_bitmap(b.bitmap, options.Tint.color, centerX, centerY, C.float(left), C.float(top), C.float(options.Rotation.Angle), 0)
 			} else {
 				C.al_draw_tinted_bitmap(b.bitmap, options.Tint.color, C.float(left), C.float(top), 0)
 			}
 		}
+	}
 }
 
 func (b *Bitmap) Width() int {