draw/gen.go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build ignore

package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/format"
	"io/ioutil"
	"log"
	"os"
	"strings"
)

var debug = flag.Bool("debug", false, "")

func main() {
	flag.Parse()

	w := new(bytes.Buffer)
	w.WriteString("// generated by \"go run gen.go\". DO NOT EDIT.\n\n" +
		"package draw\n\nimport (\n\"image\"\n\"image/color\"\n)\n")

	gen(w, "nnScaler", codeNNLeaf)
	gen(w, "ablScaler", codeABLLeaf)
	genKernel(w)

	if *debug {
		os.Stdout.Write(w.Bytes())
		return
	}
	out, err := format.Source(w.Bytes())
	if err != nil {
		log.Fatal(err)
	}
	if err := ioutil.WriteFile("impl.go", out, 0660); err != nil {
		log.Fatal(err)
	}
}

// dsTypes are the space-separated (dst image type, src image type) pairs to
// generate scale_DType_SType implementations for. The last element in the
// slice should be the fallback pair "Image image.Image".
//
// TODO: add more concrete types: *image.RGBA, *image.YCbCr, etc.
var dsTypes = []string{
	"Image image.Image",
}

type data struct {
	dType    string
	sType    string
	receiver string
}

func gen(w *bytes.Buffer, receiver string, code string) {
	expn(w, codeRoot, &data{receiver: receiver})

	for _, dsType := range dsTypes {
		dType, sType := split(dsType, " ")
		expn(w, code, &data{
			dType:    dType,
			sType:    sType,
			receiver: receiver,
		})
	}
}

func genKernel(w *bytes.Buffer) {
	expn(w, codeKernelRoot, &data{})

	dTypesSeen := map[string]bool{}
	sTypesSeen := map[string]bool{}
	for _, dsType := range dsTypes {
		dType, sType := split(dsType, " ")
		if !sTypesSeen[sType] {
			sTypesSeen[sType] = true
			expn(w, codeKernelLeafX, &data{
				sType: sType,
			})
		}
		if !dTypesSeen[dType] {
			dTypesSeen[dType] = true
			expn(w, codeKernelLeafY, &data{
				dType: dType,
			})
		}
	}
}

func expn(w *bytes.Buffer, code string, d *data) {
	for _, line := range strings.Split(code, "\n") {
		for {
			i := strings.IndexByte(line, '$')
			if i < 0 {
				break
			}
			prefix, s := line[:i], line[i+1:]

			i = len(s)
			for j, c := range s {
				if !('A' <= c && c <= 'Z' || 'a' <= c && c <= 'z') {
					i = j
					break
				}
			}
			dollar, suffix := s[:i], s[i:]

			e := expnLine(prefix, dollar, suffix, d)
			if e == "" {
				log.Fatalf("couldn't expand %q", line)
			}
			line = e
		}
		fmt.Fprintln(w, line)
	}
}

func expnLine(prefix, dollar, suffix string, d *data) string {
	switch dollar {
	case "dType":
		return prefix + d.dType + suffix
	case "dTypeRN":
		return prefix + relName(d.dType) + suffix
	case "sType":
		return prefix + d.sType + suffix
	case "sTypeRN":
		return prefix + relName(d.sType) + suffix
	case "receiver":
		return prefix + d.receiver + suffix

	case "dstColorDecl":
		if d.dType == "Image" {
			return "dstColorRGBA64 := &color.RGBA64{}\n" +
				"dstColor := color.Color(dstColorRGBA64)"
		}
		return ";"

	case "blend":
		args, _ := splitArgs(suffix)
		if len(args) != 4 {
			return ""
		}
		return fmt.Sprintf(""+
			"%sr = %s*%sr + %s*%sr\n"+
			"%sg = %s*%sg + %s*%sg\n"+
			"%sb = %s*%sb + %s*%sb\n"+
			"%sa = %s*%sa + %s*%sa",
			args[3], args[0], args[1], args[2], args[3],
			args[3], args[0], args[1], args[2], args[3],
			args[3], args[0], args[1], args[2], args[3],
			args[3], args[0], args[1], args[2], args[3],
		)

	case "outputu":
		args, _ := splitArgs(suffix)
		if len(args) != 3 {
			return ""
		}
		switch d.dType {
		default:
			log.Fatalf("bad dType %q", d.dType)
		case "Image":
			return fmt.Sprintf(""+
				"dstColorRGBA64.R = uint16(%sr)\n"+
				"dstColorRGBA64.G = uint16(%sg)\n"+
				"dstColorRGBA64.B = uint16(%sb)\n"+
				"dstColorRGBA64.A = uint16(%sa)\n"+
				"dst.Set(dp.X+int(%s), dp.Y+int(%s), dstColor)",
				args[2], args[2], args[2], args[2],
				args[0], args[1],
			)
		}

	case "outputf":
		args, _ := splitArgs(suffix)
		if len(args) != 4 {
			return ""
		}
		switch d.dType {
		default:
			log.Fatalf("bad dType %q", d.dType)
		case "Image":
			return fmt.Sprintf(""+
				"dstColorRGBA64.R = ftou(%sr * %s)\n"+
				"dstColorRGBA64.G = ftou(%sg * %s)\n"+
				"dstColorRGBA64.B = ftou(%sb * %s)\n"+
				"dstColorRGBA64.A = ftou(%sa * %s)\n"+
				"dst.Set(dp.X+int(%s), dp.Y+int(%s), dstColor)",
				args[2], args[3], args[2], args[3], args[2], args[3], args[2], args[3],
				args[0], args[1],
			)
		}

	case "srcf", "srcu":
		lhs, eqOp := splitEq(prefix)
		if lhs == "" {
			return ""
		}
		args, extra := splitArgs(suffix)
		if len(args) != 2 {
			return ""
		}

		tmp := ""
		if dollar == "srcf" {
			tmp = "u"
		}

		buf := new(bytes.Buffer)
		switch d.sType {
		default:
			log.Fatalf("bad sType %q", d.sType)
		case "image.Image":
			fmt.Fprintf(buf, "%sr%s, %sg%s, %sb%s, %sa%s := "+
				"src.At(sp.X + int(%s), sp.Y+int(%s)).RGBA()\n",
				lhs, tmp, lhs, tmp, lhs, tmp, lhs, tmp, args[0], args[1])
		}

		if dollar == "srcf" {
			fmt.Fprintf(buf, ""+
				"%sr %s float64(%sru)%s\n"+
				"%sg %s float64(%sgu)%s\n"+
				"%sb %s float64(%sbu)%s\n"+
				"%sa %s float64(%sau)%s\n",
				lhs, eqOp, lhs, extra,
				lhs, eqOp, lhs, extra,
				lhs, eqOp, lhs, extra,
				lhs, eqOp, lhs, extra,
			)
		}

		return strings.TrimSpace(buf.String())
	}
	return ""
}

func split(s, sep string) (string, string) {
	if i := strings.Index(s, sep); i >= 0 {
		return strings.TrimSpace(s[:i]), strings.TrimSpace(s[i+len(sep):])
	}
	return "", ""
}

func splitEq(s string) (lhs, eqOp string) {
	s = strings.TrimSpace(s)
	if lhs, _ = split(s, ":="); lhs != "" {
		return lhs, ":="
	}
	if lhs, _ = split(s, "+="); lhs != "" {
		return lhs, "+="
	}
	return "", ""
}

func splitArgs(s string) (args []string, extra string) {
	s = strings.TrimSpace(s)
	if s == "" || s[0] != '[' {
		return nil, ""
	}
	s = s[1:]

	i := strings.IndexByte(s, ']')
	if i < 0 {
		return nil, ""
	}
	args, extra = strings.Split(s[:i], ","), s[i+1:]
	for i := range args {
		args[i] = strings.TrimSpace(args[i])
	}
	return args, extra
}

func relName(s string) string {
	if i := strings.LastIndex(s, "."); i >= 0 {
		return s[i+1:]
	}
	return s
}

const (
	codeRoot = `
		func (z *$receiver) Scale(dst Image, dp image.Point, src image.Image, sp image.Point) {
			if z.dw <= 0 || z.dh <= 0 || z.sw <= 0 || z.sh <= 0 {
				return
			}
			// TODO: generate type switches for the different dsTypes.
			z.scale_Image_Image(dst, dp, src, sp)
		}
	`

	codeNNLeaf = `
		func (z *nnScaler) scale_$dTypeRN_$sTypeRN(dst $dType, dp image.Point, src $sType, sp image.Point) {
			$dstColorDecl
			for dy := int32(0); dy < z.dh; dy++ {
				sy := (2*uint64(dy) + 1) * uint64(z.sh) / (2 * uint64(z.dh))
				for dx := int32(0); dx < z.dw; dx++ {
					sx := (2*uint64(dx) + 1) * uint64(z.sw) / (2 * uint64(z.dw))
					p := $srcu[sx, sy]
					$outputu[dx, dy, p]
				}
			}
		}
	`

	codeABLLeaf = `
		func (z *ablScaler) scale_$dTypeRN_$sTypeRN(dst $dType, dp image.Point, src $sType, sp image.Point) {
			yscale := float64(z.sh) / float64(z.dh)
			xscale := float64(z.sw) / float64(z.dw)
			$dstColorDecl
			for dy := int32(0); dy < z.dh; dy++ {
				sy := (float64(dy)+0.5)*yscale - 0.5
				sy0 := int32(sy)
				yFrac0 := sy - float64(sy0)
				yFrac1 := 1 - yFrac0
				sy1 := sy0 + 1
				if sy < 0 {
					sy0, sy1 = 0, 0
					yFrac0, yFrac1 = 0, 1
				} else if sy1 >= z.sh {
					sy1 = sy0
					yFrac0, yFrac1 = 1, 0
				}
				for dx := int32(0); dx < z.dw; dx++ {
					sx := (float64(dx)+0.5)*xscale - 0.5
					sx0 := int32(sx)
					xFrac0 := sx - float64(sx0)
					xFrac1 := 1 - xFrac0
					sx1 := sx0 + 1
					if sx < 0 {
						sx0, sx1 = 0, 0
						xFrac0, xFrac1 = 0, 1
					} else if sx1 >= z.sw {
						sx1 = sx0
						xFrac0, xFrac1 = 1, 0
					}
					s00 := $srcf[sx0, sy0]
					s10 := $srcf[sx1, sy0]
					$blend[xFrac1, s00, xFrac0, s10]
					s01 := $srcf[sx0, sy1]
					s11 := $srcf[sx1, sy1]
					$blend[xFrac1, s01, xFrac0, s11]
					$blend[yFrac1, s10, yFrac0, s11]
					$outputu[dx, dy, s11]
				}
			}
		}
	`

	codeKernelRoot = `
		func (z *kernelScaler) Scale(dst Image, dp image.Point, src image.Image, sp image.Point) {
			if z.dw <= 0 || z.dh <= 0 || z.sw <= 0 || z.sh <= 0 {
				return
			}
			// Create a temporary buffer:
			// scaleX distributes the source image's columns over the temporary image.
			// scaleY distributes the temporary image's rows over the destination image.
			// TODO: is it worth having a sync.Pool for this temporary buffer?
			tmp := make([][4]float64, z.dw*z.sh)
			// TODO: generate type switches for the different dTypes and sTypes.
			z.scaleX_Image(tmp, src, sp)
			z.scaleY_Image(dst, dp, tmp)
		}
	`

	codeKernelLeafX = `
		func (z *kernelScaler) scaleX_$sTypeRN(tmp [][4]float64, src $sType, sp image.Point) {
			t := 0
			for y := int32(0); y < z.sh; y++ {
				for _, s := range z.horizontal.sources {
					var pr, pg, pb, pa float64
					for _, c := range z.horizontal.contribs[s.i:s.j] {
						p += $srcf[c.coord, y] * c.weight
					}
					tmp[t] = [4]float64{
						pr * s.invTotalWeightFFFF,
						pg * s.invTotalWeightFFFF,
						pb * s.invTotalWeightFFFF,
						pa * s.invTotalWeightFFFF,
					}
					t++
				}
			}
		}
	`

	codeKernelLeafY = `
		func (z *kernelScaler) scaleY_$dTypeRN(dst $dType, dp image.Point, tmp [][4]float64) {
			$dstColorDecl
			for x := int32(0); x < z.dw; x++ {
				for y, s := range z.vertical.sources {
					var pr, pg, pb, pa float64
					for _, c := range z.vertical.contribs[s.i:s.j] {
						p := &tmp[c.coord*z.dw+x]
						pr += p[0] * c.weight
						pg += p[1] * c.weight
						pb += p[2] * c.weight
						pa += p[3] * c.weight
					}
					$outputf[x, y, p, s.invTotalWeight]
				}
			}
		}
	`
)