transform.go

package vips

import (
	"bytes"
	"io"
	"math"
	"os"
)

// InputParams are options when importing an image from file or buffer
type InputParams struct {
	InputFile string
	Reader    io.Reader
}

// TransformParams are parameters for the transformation
type TransformParams struct {
	PadStrategy             Extend
	ResizeStrategy          ResizeStrategy
	CropAnchor              Anchor
	ReductionSampler        Kernel
	EnlargementInterpolator Interpolator
	ZoomX                   int
	ZoomY                   int
	Invert                  bool
	BlurSigma               float64
	Flip                    FlipDirection
	Width                   Scalar
	Height                  Scalar
	CropOffsetX             Scalar
	CropOffsetY             Scalar
}

// Transform handles single image transformations
type Transform struct {
	input        *InputParams
	tx           *TransformParams
	export       *ExportParams
	targetWidth  int
	targetHeight int
	cropOffsetX  int
	cropOffsetY  int
}

// NewTransform constructs a new transform for execution
func NewTransform() *Transform {
	return &Transform{
		input: &InputParams{},
		tx: &TransformParams{
			ResizeStrategy:          ResizeStrategyAuto,
			CropAnchor:              AnchorAuto,
			ReductionSampler:        KernelLanczos3,
			EnlargementInterpolator: InterpolateBicubic,
		},
		export: &ExportParams{
			Format:         ImageTypeUnknown,
			Quality:        90,
			Interpretation: InterpretationSRGB,
		},
	}
}

// LoadFile loads a file into the transform
func (t *Transform) LoadFile(file string) *Transform {
	t.input.Reader = LazyOpen(file)
	return t
}

// LoadBuffer loads a buffer into the transform
func (t *Transform) LoadBuffer(buf []byte) *Transform {
	t.input.Reader = bytes.NewBuffer(buf)
	return t
}

// Load loads a buffer into the transform
func (t *Transform) Load(reader io.Reader) *Transform {
	t.input.Reader = reader
	return t
}

// Output outputs the transform to a buffer and closes it
func (t *Transform) Output(writer io.Writer) *Transform {
	t.export.Writer = writer
	return t
}

// OutputBytes outputs the transform to a buffer and closes it
func (t *Transform) OutputBytes() *Transform {
	t.export.Writer = nil
	return t
}

// OutputFile outputs the transform to a file and closes it
func (t *Transform) OutputFile(file string) *Transform {
	t.export.Writer = LazyCreate(file)
	return t
}

// Zoom an image by repeating pixels. This is fast nearest-neighbour zoom.
func (t *Transform) Zoom(x, y int) *Transform {
	t.tx.ZoomX = x
	t.tx.ZoomY = y
	return t
}

// Anchor sets the anchor for cropping
func (t *Transform) Anchor(anchor Anchor) *Transform {
	t.tx.CropAnchor = anchor
	return t
}

// CropOffsetX sets the target offset from the crop position
func (t *Transform) CropOffsetX(x int) *Transform {
	t.tx.CropOffsetX.SetInt(x)
	return t
}

// CropOffsetY sets the target offset from the crop position
func (t *Transform) CropOffsetY(y int) *Transform {
	t.tx.CropOffsetY.SetInt(y)
	return t
}

// CropRelativeOffsetX sets the target offset from the crop position
func (t *Transform) CropRelativeOffsetX(x float64) *Transform {
	t.tx.CropOffsetX.SetScale(x)
	return t
}

// CropRelativeOffsetY sets the target offset from the crop position
func (t *Transform) CropRelativeOffsetY(y float64) *Transform {
	t.tx.CropOffsetY.SetScale(y)
	return t
}

// Kernel sets the sampling kernel for the transform when down-scaling. Defaults to lancosz3
func (t *Transform) Kernel(kernel Kernel) *Transform {
	t.tx.ReductionSampler = kernel
	return t
}

// Interpolator sets the resampling interpolator when upscaling, defaults to bicubic
func (t *Transform) Interpolator(interp Interpolator) *Transform {
	t.tx.EnlargementInterpolator = interp
	return t
}

// ResizeStrategy sets the strategy when resizing an image
func (t *Transform) ResizeStrategy(strategy ResizeStrategy) *Transform {
	t.tx.ResizeStrategy = strategy
	return t
}

// PadStrategy sets the strategy when the image must be padded to maintain aspect ratoi
func (t *Transform) PadStrategy(strategy Extend) *Transform {
	t.tx.PadStrategy = strategy
	return t
}

// Invert inverts the image color
func (t *Transform) Invert() *Transform {
	t.tx.Invert = true
	return t
}

// Flip flips the image horizontally or vertically
func (t *Transform) Flip(flip FlipDirection) *Transform {
	t.tx.Flip = flip
	return t
}

// GaussBlur applies a gaussian blur to the image
func (t *Transform) GaussBlur(sigma float64) *Transform {
	t.tx.BlurSigma = sigma
	return t
}

// Embed this image appropriately if resized according to a new aspect ratio
func (t *Transform) Embed(extend Extend) *Transform {
	t.tx.ResizeStrategy = ResizeStrategyEmbed
	t.tx.PadStrategy = extend
	return t
}

// Crop an image, width and height must be equal to or less than image size
func (t *Transform) Crop(anchor Anchor) *Transform {
	t.tx.ResizeStrategy = ResizeStrategyCrop
	return t
}

// Stretch an image without maintaining aspect ratio
func (t *Transform) Stretch() *Transform {
	t.tx.ResizeStrategy = ResizeStrategyCrop
	return t
}

// ScaleWidth scales the image by its width proportionally
func (t *Transform) ScaleWidth(scale float64) *Transform {
	t.tx.Width.SetScale(scale)
	return t
}

// ScaleHeight scales the height of the image proportionally
func (t *Transform) ScaleHeight(scale float64) *Transform {
	t.tx.Height.SetScale(scale)
	return t
}

// Scale the image
func (t *Transform) Scale(scale float64) *Transform {
	t.tx.Width.SetScale(scale)
	t.tx.Height.SetScale(scale)
	return t
}

// ResizeWidth resizes the image to the given width, maintaining aspect ratio
func (t *Transform) ResizeWidth(width int) *Transform {
	t.tx.Width.SetInt(width)
	return t
}

// ResizeHeight resizes the image to the given height, maintaining aspect ratio
func (t *Transform) ResizeHeight(height int) *Transform {
	t.tx.Height.SetInt(height)
	return t
}

// Resize resizes the image to the given width and height
func (t *Transform) Resize(width, height int) *Transform {
	t.tx.Width.SetInt(width)
	t.tx.Height.SetInt(height)
	return t
}

// Format sets the image format of the input image when exporting. Defaults to JPEG
func (t *Transform) Format(format ImageType) *Transform {
	t.export.Format = format
	return t
}

// Quality sets the quality value for image formats that support it
func (t *Transform) Quality(quality int) *Transform {
	t.export.Quality = quality
	return t
}

// StripMetadata strips ICC profile and metadata from the image
func (t *Transform) StripMetadata() *Transform {
	t.export.StripProfile = true
	t.export.StripMetadata = true
	return t
}

// Apply loads the image, applies the transform, and exports it according
// to the parameters specified
func (t *Transform) Apply() ([]byte, error) {
	defer ShutdownThread()
	startupIfNeeded()

	image, err := t.importImage()
	if err != nil {
		return nil, err
	}

	defer image.Close()

	err = t.transform(image)
	if err != nil {
		return nil, err
	}

	return t.exportImage(image)
}

func (t *Transform) importImage() (*ImageRef, error) {
	if t.input.Reader == nil {
		panic("no input source specified")
	}
	return LoadImage(t.input.Reader)
}

func (t *Transform) exportImage(image *ImageRef) ([]byte, error) {
	if t.export.Format == ImageTypeUnknown {
		t.export.Format = image.Format()
	}

	buf, err := vipsExportBuffer(image.Image(), t.export)
	if err != nil {
		return nil, err
	}

	if t.export.Writer != nil {
		_, err = t.export.Writer.Write(buf)
		if err != nil {
			return buf, err
		}
	}

	return buf, err
}

type Blackboard struct {
	*TransformParams
	image        *ImageRef
	aspectRatio  float64
	targetWidth  int
	targetHeight int
	targetScale  float64
	cropOffsetX  int
	cropOffsetY  int
}

func NewBlackboard(image *ImageRef, p *TransformParams) *Blackboard {
	bb := &Blackboard{
		TransformParams: p,
		image:           image,
	}
	imageWidth := image.Width()
	imageHeight := image.Height()
	bb.aspectRatio = ratio(imageWidth, imageHeight)
	bb.cropOffsetX = p.CropOffsetX.GetRounded(imageWidth)
	bb.cropOffsetY = p.CropOffsetY.GetRounded(imageHeight)

	if p.Width.Value == 0 && p.Height.Value == 0 {
		return bb
	}

	bb.targetWidth = p.Width.GetRounded(imageWidth)
	bb.targetHeight = p.Height.GetRounded(imageHeight)

	switch {
	case bb.targetWidth > 0 && bb.targetHeight > 0:
		// Nothing to do
	case bb.targetWidth > 0:
		bb.targetHeight = roundFloat(ratio(bb.targetWidth, imageWidth) * float64(imageHeight))
	case bb.targetHeight > 0:
		bb.targetWidth = roundFloat(ratio(bb.targetHeight, imageHeight) * float64(imageWidth))
	}

	if p.Width.Relative && p.Height.Relative {
		sx, sy := p.Width.Value, p.Height.Value
		if sx == 0 {
			sx = sy
		} else if sy == 0 {
			sy = sx
		}
		if sx == sy {
			bb.targetScale = sx
		}
	}
	return bb
}

func (bb *Blackboard) Width() int {
	return bb.image.Width()
}

func (bb *Blackboard) Height() int {
	return bb.image.Height()
}

func (t *Transform) transform(image *ImageRef) error {
	bb := NewBlackboard(image, t.tx)
	if err := resize(bb); err != nil {
		return err
	}

	if err := postProcess(bb); err != nil {
		return err
	}

	// TODO(d): Flatten image backgrounds (e.g., PNG)

	return nil
}

func resize(bb *Blackboard) error {
	kernel := bb.ReductionSampler

	// Check for the simple scale down cases
	if bb.targetScale != 0 {
		return bb.image.Resize(bb.targetScale, InputInt("kernel", int(kernel)))
	}

	if bb.targetHeight == 0 && bb.targetWidth == 0 {
		return nil
	}

	shrinkX := ratio(bb.Width(), bb.targetWidth)
	shrinkY := ratio(bb.Height(), bb.targetHeight)

	cropMode := bb.ResizeStrategy == ResizeStrategyCrop
	stretchMode := bb.ResizeStrategy == ResizeStrategyStretch

	if !stretchMode {
		if shrinkX > 0 && shrinkY > 0 {
			if cropMode {
				shrinkX = math.Min(shrinkX, shrinkY)
			} else {
				shrinkX = math.Max(shrinkX, shrinkY)
			}
		} else {
			if cropMode {
				shrinkX = math.Min(shrinkX, shrinkY)
			} else {
				shrinkX = math.Max(shrinkX, shrinkY)
			}
		}
		shrinkY = shrinkX
	}

	if shrinkX != 1 || shrinkY != 1 {
		if err := bb.image.Resize(
			1.0/shrinkX,
			InputDouble("vscale", 1.0/shrinkY),
			InputInt("kernel", int(kernel)),
		); err != nil {
			return err
		}

		// If stretching then we're done.
		if stretchMode {
			return nil
		}
	}

	// Crop if necessary
	if cropMode {
		if err := maybeCrop(bb); err != nil {
			return err
		}
	}

	if err := maybeEmbed(bb); err != nil {
		return err
	}

	return nil
}

func maybeCrop(bb *Blackboard) error {
	imageW, imageH := bb.Width(), bb.Height()

	if bb.targetWidth >= imageW && bb.targetHeight >= imageH {
		return nil
	}

	width := minInt(bb.targetWidth, imageW)
	height := minInt(bb.targetHeight, imageH)
	left, top := 0, 0
	middleX := (imageW - bb.targetWidth + 1) >> 1
	middleY := (imageH - bb.targetHeight + 1) >> 1
	if bb.cropOffsetX != 0 || bb.cropOffsetY != 0 {
		if bb.cropOffsetX >= 0 {
			left = middleX + minInt(bb.cropOffsetX, middleX)
		} else {
			left = middleX - maxInt(bb.cropOffsetX, middleX)
		}
		if bb.cropOffsetY >= 0 {
			top = middleY + minInt(bb.cropOffsetY, middleY)
		} else {
			top = middleY - maxInt(bb.cropOffsetY, middleY)
		}
	} else {
		switch bb.CropAnchor {
		case AnchorTop:
			left = middleX
		case AnchorBottom:
			left = middleX
			top = imageH - bb.targetHeight
		case AnchorRight:
			left = imageW - bb.targetWidth
			top = middleY
		case AnchorLeft:
			top = middleY
		case AnchorTopRight:
			left = imageW - bb.targetWidth
		case AnchorTopLeft:
		case AnchorBottomRight:
			left = imageW - bb.targetWidth
			top = imageH - bb.targetHeight
		case AnchorBottomLeft:
			top = imageH - bb.targetHeight
		default:
			left = middleX
			top = middleY
		}
	}
	left = maxInt(left, 0)
	top = maxInt(top, 0)
	if left+width > imageW {
		width = imageW - left
		bb.targetWidth = width
	}
	if top+height > imageH {
		height = imageH - top
		bb.targetHeight = height
	}
	return bb.image.ExtractArea(left, top, width, height)
}

func maybeEmbed(bb *Blackboard) error {
	imageW, imageH := bb.Width(), bb.Height()

	// Now we might need to embed to match the target dimensions
	if bb.targetWidth > imageW || bb.targetHeight > imageH {
		var left, top int
		width, height := imageW, imageH
		if bb.targetWidth > imageW {
			width = bb.targetWidth
			left = (bb.targetWidth - imageW) >> 1
		}
		if bb.targetHeight > imageH {
			height = bb.targetHeight
			top = (bb.targetHeight - imageH) >> 1
		}
		if err := bb.image.Embed(left, top, width, height, InputInt("extend", int(bb.PadStrategy))); err != nil {
			return err
		}
	}

	return nil
}

func postProcess(bb *Blackboard) error {
	if bb.ZoomX > 0 || bb.ZoomY > 0 {
		if err := bb.image.Zoom(bb.ZoomX, bb.ZoomY); err != nil {
			return err
		}
	}

	if bb.Flip != FlipNone {
		var err error
		switch bb.Flip {
		case FlipHorizontal:
			err = bb.image.Flip(DirectionHorizontal)
		case FlipVertical:
			err = bb.image.Flip(DirectionVertical)
		case FlipBoth:
			err = bb.image.Flip(DirectionHorizontal)
			if err == nil {
				err = bb.image.Flip(DirectionVertical)
			}
		}
		if err != nil {
			return err
		}
	}

	if bb.Invert {
		if err := bb.image.Invert(); err != nil {
			return err
		}
	}

	if bb.BlurSigma > 0 {
		if err := bb.image.Gaussblur(bb.BlurSigma); err != nil {
			return err
		}
	}

	return nil
}

func minInt(a, b int) int {
	return int(math.Min(float64(a), float64(b)))
}

func maxInt(a, b int) int {
	return int(math.Max(float64(a), float64(b)))
}

func ratio(x, y int) float64 {
	if x == y {
		return 1
	}
	return float64(x) / float64(y)
}

func roundFloat(f float64) int {
	if f < 0 {
		return int(math.Ceil(f - 0.5))
	}
	return int(math.Floor(f + 0.5))
}

// LazyFile is a lazy reader or writer
// TODO(d): Move this to AF
type LazyFile struct {
	name string
	file *os.File
}

func LazyOpen(file string) io.Reader {
	return &LazyFile{name: file}
}

func LazyCreate(file string) io.Writer {
	return &LazyFile{name: file}
}

func (r *LazyFile) Read(p []byte) (n int, err error) {
	if r.file == nil {
		f, err := os.Open(r.name)
		if err != nil {
			return 0, err
		}
		r.file = f
	}
	return r.file.Read(p)
}

func (r *LazyFile) Close() error {
	if r.file != nil {
		r.file.Close()
		r.file = nil
	}
	return nil
}

func (r *LazyFile) Write(p []byte) (n int, err error) {
	if r.file == nil {
		f, err := os.Create(r.name)
		if err != nil {
			return 0, err
		}
		r.file = f
	}
	return r.file.Write(p)
}

type Scalar struct {
	Value    float64
	Relative bool
}

func (s *Scalar) SetInt(value int) {
	s.Set(float64(value))
}

func (s *Scalar) Set(value float64) {
	s.Value = value
	s.Relative = false
}

func (s *Scalar) SetScale(f float64) {
	s.Value = f
	s.Relative = true
}

func (s *Scalar) Get(base int) float64 {
	if s.Relative {
		return s.Value * float64(base)
	}
	return s.Value
}

func (s *Scalar) GetRounded(base int) int {
	return roundFloat(s.Get(base))
}