imagefn - scale.go

     1  package imagefn
     2  
     3  import (
     4  	"image"
     5  	"image/color"
     6  )
     7  
     8  type scale struct {
     9  	image.Image
    10  	ScaleX, ScaleY float64
    11  }
    12  
    13  func Scale(i image.Image, xScale, yScale float64) image.Image {
    14  	switch im := i.(type) {
    15  	case *empty:
    16  		return i
    17  	case *scale:
    18  		xScale *= im.ScaleX
    19  		yScale *= im.ScaleY
    20  		i = im.Image
    21  	}
    22  	if xScale < 0 {
    23  		if yScale < 0 {
    24  			i = FlipX(i)
    25  		} else {
    26  			i = Rotate180(i)
    27  			yScale = -yScale
    28  		}
    29  		xScale = -xScale
    30  	} else if yScale < 0 {
    31  		i = FlipY(i)
    32  		yScale = -yScale
    33  	}
    34  	if xScale == 0 || yScale == 0 {
    35  		return newEmpty(i)
    36  	}
    37  	if xScale == 1 && yScale == 1 {
    38  		return i
    39  	}
    40  	return &scale{
    41  		Image:  i,
    42  		ScaleX: xScale,
    43  		ScaleY: yScale,
    44  	}
    45  }
    46  
    47  func ScaleDimensions(i image.Image, x, y int) image.Image {
    48  	b := i.Bounds()
    49  	return Scale(i, float64(x)/float64(b.Dx()), float64(y)/float64(b.Dy()))
    50  }
    51  
    52  func (s *scale) Bounds() image.Rectangle {
    53  	b := s.Image.Bounds()
    54  	return image.Rect(
    55  		b.Min.X,
    56  		b.Min.Y,
    57  		b.Min.X+int(float64(b.Dx())/s.ScaleX),
    58  		b.Min.Y+int(float64(b.Dy())/s.ScaleY),
    59  	)
    60  }
    61  
    62  func (s *scale) At(x, y int) color.Color {
    63  	b := s.Image.Bounds()
    64  	return s.Image.At(
    65  		b.Min.X+int(float64(x-b.Min.X)/s.ScaleX),
    66  		b.Min.Y+int(float64(y-b.Min.Y)/s.ScaleY),
    67  	)
    68  }
    69  
    70  type Scaler interface {
    71  	At(image.Image, int, int) color.Color
    72  }
    73  
    74  type smoothScale struct {
    75  	scale
    76  	scaler Scaler
    77  }
    78  
    79  func SmoothScale(i image.Image, xScale, yScale float64, scaler Scaler) image.Image {
    80  	switch s := Scale(i, xScale, yScale).(type) {
    81  	case *scale:
    82  		return &smoothScale{*s, scaler}
    83  	default:
    84  		return s
    85  	}
    86  }
    87  
    88  func SmoothScaleDimensions(i image.Image, x, y int, scaler Scaler) image.Image {
    89  	b := i.Bounds()
    90  	return SmoothScale(i, float64(x)/float64(b.Dx()), float64(y)/float64(b.Dy()), scaler)
    91  }
    92  
    93  func (s *smoothScale) At(x, y int) color.Color {
    94  	return s.ColorModel().Convert(s.scaler.At(s.Image, x, y))
    95  }