zntg/allegro5/bitmap.go

package allegro5

// #include <allegro5/allegro.h>
// #include <stdlib.h>
import "C"

import (
	"errors"
	"image"
	"image/color"
	"unsafe"
)

// Bitmap represents an in memory bitmap
type Bitmap struct {
	bitmap *C.ALLEGRO_BITMAP
	width  int
	height int
}

type DrawOptions struct {
	Center   bool
	Scale    Scale
	Tint     *Color
	Rotation *Rotation
}

type Scale interface {
	Horizontal() 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
func NewBitmap(width, height int) (*Bitmap, error) {
	b := C.al_create_bitmap(C.int(width), C.int(height))
	if nil == b {
		return nil, errors.New("error creating bitmap")
	}
	return &Bitmap{b, width, height}, nil
}

// NewBitmapFromImage creates a new bitmap starting from a Go native image (image.Image)
func NewBitmapFromImage(im image.Image) (*Bitmap, error) {
	var bnd = im.Bounds()
	width, height := bnd.Dx(), bnd.Dy()
	bmp, err := NewBitmap(width, height)
	if nil != err {
		return nil, err
	}
	row := make([]uint8, width*4)
	rgn := C.al_lock_bitmap(bmp.bitmap, C.ALLEGRO_PIXEL_FORMAT_ABGR_8888, C.ALLEGRO_LOCK_WRITEONLY)
	if nil == rgn {
		bmp.Destroy()
		return nil, errors.New("unable to lock bitmap")
	}
	data := (*[1 << 30]uint8)(rgn.data)
	offset := 0
	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			pix := color.RGBAModel.Convert(im.At(x, y)).(color.RGBA)
			row[x*4] = pix.R
			row[x*4+1] = pix.G
			row[x*4+2] = pix.B
			row[x*4+3] = pix.A
		}
		copy(data[offset:], row)
		offset += int(rgn.pitch)
	}
	C.al_unlock_bitmap(bmp.bitmap)
	return bmp, nil
}

// LoadBitmap tries to load the image at the specified path as a bitmap
func LoadBitmap(path string) (*Bitmap, error) {
	p := C.CString(path)
	defer C.free(unsafe.Pointer(p))
	b := C.al_load_bitmap(p)
	if nil == b {
		return nil, errors.New("error loading bitmap")
	}
	width := int(C.al_get_bitmap_width(b))
	height := int(C.al_get_bitmap_height(b))
	return &Bitmap{b, width, height}, nil
}

// Draw draws the bitmap at the given location
func (b *Bitmap) Draw(left, top float32) {
	C.al_draw_bitmap(b.bitmap, C.float(left), C.float(top), 0)
}

func (b *Bitmap) DrawOptions(left, top float32, options DrawOptions) {
	width := float32(b.width)
	height := float32(b.height)

	scale := nil != options.Scale
	if scale {
		width *= options.Scale.Horizontal()
		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 { // 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 { // 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 {
	return b.width
}

func (b *Bitmap) Height() int {
	return b.height
}

// Destroy destroys the bitmap
func (b *Bitmap) Destroy() {
	C.al_destroy_bitmap(b.bitmap)
}