Support for unstyled, path-only SVG images of the type generated by the jSignature web control.

1 files changed, 210 insertions, 0 deletions

diff --git a/svgbasic.go b/svgbasic.go
new file mode 100644
index 0000000..4c58f95
--- /dev/null
+++ b/svgbasic.go
@@ -0,0 +1,210 @@
+/*
+ * Copyright (c) 2014 Kurt Jung (Gmail: kurt.w.jung)
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+package gofpdf
+
+import (
+	"encoding/xml"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+var pathCmdSub *strings.Replacer
+
+func init() {
+	// Handle permitted constructions like "100L200,230"
+	pathCmdSub = strings.NewReplacer(",", " ",
+		"L", " L ", "l", " l ",
+		"C", " C ", "c", " c ",
+		"M", " M ", "m", " m ")
+}
+
+// SvgBasicSegmentType describes a single curve or position segment
+type SvgBasicSegmentType struct {
+	Cmd byte // See http://www.w3.org/TR/SVG/paths.html for path command structure
+	Arg [6]float64
+}
+
+func absolutizePath(segs []SvgBasicSegmentType) {
+	var x, y float64
+	var segPtr *SvgBasicSegmentType
+	adjust := func(pos int, adjX, adjY float64) {
+		segPtr.Arg[pos] += adjX
+		segPtr.Arg[pos+1] += adjY
+	}
+	for j, seg := range segs {
+		segPtr = &segs[j]
+		if j == 0 && seg.Cmd == 'm' {
+			segPtr.Cmd = 'M'
+		}
+		switch segPtr.Cmd {
+		case 'M':
+			x = seg.Arg[0]
+			y = seg.Arg[1]
+		case 'm':
+			adjust(0, x, y)
+			segPtr.Cmd = 'M'
+			x = segPtr.Arg[0]
+			y = segPtr.Arg[1]
+		case 'L':
+			x = seg.Arg[0]
+			y = seg.Arg[1]
+		case 'l':
+			adjust(0, x, y)
+			segPtr.Cmd = 'L'
+			x = segPtr.Arg[0]
+			y = segPtr.Arg[1]
+		case 'C':
+			x = seg.Arg[4]
+			y = seg.Arg[5]
+		case 'c':
+			adjust(0, x, y)
+			adjust(2, x, y)
+			adjust(4, x, y)
+			segPtr.Cmd = 'C'
+			x = segPtr.Arg[4]
+			y = segPtr.Arg[5]
+		}
+	}
+}
+
+func pathParse(pathStr string) (segs []SvgBasicSegmentType, err error) {
+	var seg SvgBasicSegmentType
+	var j, argJ, argCount, prevArgCount int
+	setup := func(n int) {
+		// It is not strictly necessary to clear arguments, but result may be clearer
+		// to caller
+		for j := 0; j < len(seg.Arg); j++ {
+			seg.Arg[j] = 0.0
+		}
+		argJ = 0
+		argCount = n
+		prevArgCount = n
+	}
+	var str string
+	var c byte
+	pathStr = pathCmdSub.Replace(pathStr)
+	strList := strings.Fields(pathStr)
+	count := len(strList)
+	for j = 0; j < count && err == nil; j++ {
+		str = strList[j]
+		if argCount == 0 { // Look for path command or argument continuation
+			c = str[0]
+			if c == '-' || (c >= '0' && c <= '9') { // More arguments
+				if j > 0 {
+					setup(prevArgCount)
+					// Repeat previous action
+					if seg.Cmd == 'M' {
+						seg.Cmd = 'L'
+					} else if seg.Cmd == 'm' {
+						seg.Cmd = 'l'
+					}
+				} else {
+					err = fmt.Errorf("expecting SVG path command at first position, got %s", str)
+				}
+			}
+		}
+		if err == nil {
+			if argCount == 0 {
+				seg.Cmd = str[0]
+				switch seg.Cmd {
+				case 'M', 'm': // Absolute/relative moveto: x, y
+					setup(2)
+				case 'C', 'c': // Absolute/relative Bézier curve: cx0, cy0, cx1, cy1, x1, y1
+					setup(6)
+				case 'L', 'l': // Absolute/relative lineto: x, y
+					setup(2)
+				default:
+					err = fmt.Errorf("expecting SVG path command at position %d, got %s", j, str)
+				}
+			} else {
+				seg.Arg[argJ], err = strconv.ParseFloat(str, 64)
+				if err == nil {
+					argJ++
+					argCount--
+					if argCount == 0 {
+						segs = append(segs, seg)
+					}
+				}
+			}
+		}
+	}
+	if err == nil {
+		if argCount == 0 {
+			absolutizePath(segs)
+		} else {
+			err = fmt.Errorf("Expecting additional (%d) numeric arguments", argCount)
+		}
+	}
+	return
+}
+
+// SvgBasicType aggregates the information needed to describe a multi-segment
+// basic vector image
+type SvgBasicType struct {
+	Wd, Ht   float64
+	Segments [][]SvgBasicSegmentType
+}
+
+// SvgBasicParse parses a simple scalable vector graphics (SVG) buffer into a
+// descriptor. Only a small subset of the SVG standard, in particular the path
+// information generated by jSignature, is supported. The returned path data
+// includes only the commands 'M' (absolute moveto: x, y), 'L' (absolute
+// lineto: x, y), and 'C' (absolute cubic Bézier curve: cx0, cy0, cx1, cy1,
+// x1,y1).
+func SvgBasicParse(buf []byte) (sig SvgBasicType, err error) {
+	type pathType struct {
+		D string `xml:"d,attr"`
+	}
+	type srcType struct {
+		Wd    float64    `xml:"width,attr"`
+		Ht    float64    `xml:"height,attr"`
+		Paths []pathType `xml:"path"`
+	}
+	var src srcType
+	err = xml.Unmarshal(buf, &src)
+	if err == nil {
+		if src.Wd > 0 && src.Ht > 0 {
+			sig.Wd, sig.Ht = src.Wd, src.Ht
+			var segs []SvgBasicSegmentType
+			for _, path := range src.Paths {
+				if err == nil {
+					segs, err = pathParse(path.D)
+					if err == nil {
+						sig.Segments = append(sig.Segments, segs)
+					}
+				}
+			}
+		} else {
+			err = fmt.Errorf("Unacceptable values for basic SVG extent: %.2f x %.2f",
+				sig.Wd, sig.Ht)
+		}
+	}
+	return
+}
+
+// SvgBasicParse parses a simple scalable vector graphics (SVG) file into a
+// basic descriptor. See SvgBasicParse for additional comments.
+func SvgBasicFileParse(svgFileStr string) (sig SvgBasicType, err error) {
+	var buf []byte
+	buf, err = ioutil.ReadFile(svgFileStr)
+	if err == nil {
+		sig, err = SvgBasicParse(buf)
+	}
+	return
+}