Lawrence Kesteloot provided code to allow an image's extent to be determined prior to placement.

4 files changed, 84 insertions, 20 deletions

diff --git a/def.go b/def.go
index 5d7edfd..afdc9f2 100644
--- a/def.go
+++ b/def.go
@@ -61,16 +61,22 @@ type ImageInfoType struct {
 	f     string
 	dp    string
 	trns  []int
+	scale float64 // document scaling factor
+}
+
+// The width and height of the image in the units of the Fpdf object.
+func (info *ImageInfoType) Extent() (wd, ht float64) {
+	return info.w / info.scale, info.h / info.scale
 }
 
 // The width of the image in the units of the Fpdf object.
-func (info *ImageInfoType) Width(f *Fpdf) float64 {
-	return info.w / f.k
+func (info *ImageInfoType) Width() float64 {
+	return info.w / info.scale
 }
 
 // The height of the image in the units of the Fpdf object.
-func (info *ImageInfoType) Height(f *Fpdf) float64 {
-	return info.h / f.k
+func (info *ImageInfoType) Height() float64 {
+	return info.h / info.scale
 }
 
 type fontFileType struct {
diff --git a/doc.go b/doc.go
index 3ffaf13..ff372f8 100644
--- a/doc.go
+++ b/doc.go
@@ -25,7 +25,9 @@ transparency script by Martin Hall-May. Support for gradients and clipping is
 adapted from FPDF scripts by Andreas Würmser. Support for outline bookmarks is
 adapted from Olivier Plathey by Manuel Cornes. Support for transformations is
 adapted from the FPDF transformation script by Moritz Wagner and Andreas
-Würmser. Bruno Michel has provided valuable assistance with the code.
+Würmser. Lawrence Kesteloot provided code to allow an image's extent to be
+determined prior to placement. Bruno Michel has provided valuable assistance
+with the code.
 
 The FPDF website is http://www.fpdf.org/.
 
diff --git a/fpdf.go b/fpdf.go
index c5f75fe..c5100ee 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -1910,10 +1910,13 @@ func (f *Fpdf) Image(fileStr string, x, y, w, h float64, flow bool, tp string, l
 	return
 }
 
-// Registers an image, adding it to the PDF file but not adding it to the page. Use
-// Image() with the same filename to add the image to the page. Note that Image()
-// calls this function, so this function is only necessary if you need information
-// about the image. See Image() for restrictions on the image and the "tp" parameters.
+// Registers an image, adding it to the PDF file but not adding it to the page.
+// Use Image() with the same filename to add the image to the page. Note that
+// Image() calls this function, so this function is only necessary if you need
+// information about the image before placing it. See Image() for restrictions
+// on the image and the "tp" parameters.
+//
+// See tutorial 18 for an example of this function.
 func (f *Fpdf) RegisterImage(fileStr, tp string) (info *ImageInfoType) {
 	info, ok := f.images[fileStr]
 	if !ok {
@@ -2145,11 +2148,14 @@ func be16(buf []byte) int {
 	return 256*int(buf[0]) + int(buf[1])
 }
 
+func (f *Fpdf) newImageInfo() *ImageInfoType {
+	return &ImageInfoType{scale: f.k}
+}
+
 // Extract info from a JPEG file
 // Thank you, Bruno Michel, for providing this code.
 func (f *Fpdf) parsejpg(fileStr string) (info *ImageInfoType) {
-	info = &ImageInfoType{}
-
+	info = f.newImageInfo()
 	var err error
 	info.data, err = ioutil.ReadFile(fileStr)
 	if err != nil {
@@ -2204,8 +2210,7 @@ func (f *Fpdf) readByte(buf *bytes.Buffer) (val byte) {
 }
 
 func (f *Fpdf) parsepngstream(buf *bytes.Buffer) (info *ImageInfoType) {
-	info = &ImageInfoType{}
-
+	info = f.newImageInfo()
 	// 	Check signature
 	if string(buf.Next(8)) != "\x89PNG\x0d\x0a\x1a\x0a" {
 		f.err = fmt.Errorf("Not a PNG buffer")
@@ -2692,13 +2697,14 @@ func (f *Fpdf) putimage(info *ImageInfoType) {
 	// 	Soft mask
 	if len(info.smask) > 0 {
 		smask := &ImageInfoType{
-			w:    info.w,
-			h:    info.h,
-			cs:   "DeviceGray",
-			bpc:  8,
-			f:    info.f,
-			dp:   sprintf("/Predictor 15 /Colors 1 /BitsPerComponent 8 /Columns %d", int(info.w)),
-			data: info.smask,
+			w:     info.w,
+			h:     info.h,
+			cs:    "DeviceGray",
+			bpc:   8,
+			f:     info.f,
+			dp:    sprintf("/Predictor 15 /Colors 1 /BitsPerComponent 8 /Columns %d", int(info.w)),
+			data:  info.smask,
+			scale: f.k,
 		}
 		f.putimage(smask)
 	}
diff --git a/fpdf_test.go b/fpdf_test.go
index ccdf1bf..b683b9c 100644
--- a/fpdf_test.go
+++ b/fpdf_test.go
@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
 )
@@ -1083,3 +1084,52 @@ func ExampleFpdf_tutorial17() {
 	// Output:
 	// Successfully generated pdf/tutorial17.pdf
 }
+
+// Example to demonstrate Lawrence Kesteloot's image registration code.
+func ExampleFpdf_tutorial18() {
+	const (
+		margin = 10
+		wd     = 210
+		ht     = 297
+	)
+	fileList := []string{
+		"logo-gray.png",
+		"logo.jpg",
+		"logo.png",
+		"logo-rgb.png",
+		"logo-progressive.jpg",
+	}
+	var infoPtr *gofpdf.ImageInfoType
+	var fileStr string
+	var imgWd, imgHt, lf, tp float64
+	pdf := gofpdf.New("P", "mm", "A4", FONT_DIR)
+	pdf.AddPage()
+	pdf.SetMargins(10, 10, 10)
+	pdf.SetFont("Helvetica", "", 15)
+	for j, str := range fileList {
+		fileStr = filepath.Join(IMG_DIR, str)
+		infoPtr = pdf.RegisterImage(fileStr, "")
+		imgWd, imgHt = infoPtr.Extent()
+		switch j {
+		case 0:
+			lf = margin
+			tp = margin
+		case 1:
+			lf = wd - margin - imgWd
+			tp = margin
+		case 2:
+			lf = (wd - imgWd) / 2.0
+			tp = (ht - imgHt) / 2.0
+		case 3:
+			lf = margin
+			tp = ht - imgHt - margin
+		case 4:
+			lf = wd - imgWd - margin
+			tp = ht - imgHt - margin
+		}
+		pdf.Image(fileStr, lf, tp, imgWd, imgHt, false, "", 0, "")
+	}
+	pdf.OutputAndClose(docWriter(pdf, 18))
+	// Output:
+	// Successfully generated pdf/tutorial18.pdf
+}