This closes #1225, allowing insert EMF format images

5 files changed, 27 insertions, 20 deletions

diff --git a/picture.go b/picture.go
index 5e8f6b8..f8133ca 100644
--- a/picture.go
+++ b/picture.go
@@ -113,7 +113,7 @@ func (f *File) AddPicture(sheet, cell, picture, format string) error {
 	if _, err = os.Stat(picture); os.IsNotExist(err) {
 		return err
 	}
-	ext, ok := supportImageTypes[path.Ext(picture)]
+	ext, ok := supportedImageTypes[path.Ext(picture)]
 	if !ok {
 		return ErrImgExt
 	}
@@ -154,7 +154,7 @@ func (f *File) AddPicture(sheet, cell, picture, format string) error {
 func (f *File) AddPictureFromBytes(sheet, cell, format, name, extension string, file []byte) error {
 	var drawingHyperlinkRID int
 	var hyperlinkType string
-	ext, ok := supportImageTypes[extension]
+	ext, ok := supportedImageTypes[extension]
 	if !ok {
 		return ErrImgExt
 	}
@@ -366,23 +366,20 @@ func (f *File) addMedia(file []byte, ext string) string {
 // setContentTypePartImageExtensions provides a function to set the content
 // type for relationship parts and the Main Document part.
 func (f *File) setContentTypePartImageExtensions() {
-	imageTypes := map[string]bool{"jpeg": false, "png": false, "gif": false, "tiff": false}
+	imageTypes := map[string]string{"jpeg": "image/", "png": "image/", "gif": "image/", "tiff": "image/", "emf": "image/x-"}
 	content := f.contentTypesReader()
 	content.Lock()
 	defer content.Unlock()
-	for _, v := range content.Defaults {
-		_, ok := imageTypes[v.Extension]
-		if ok {
-			imageTypes[v.Extension] = true
+	for _, file := range content.Defaults {
+		if _, ok := imageTypes[file.Extension]; ok {
+			delete(imageTypes, file.Extension)
 		}
 	}
-	for k, v := range imageTypes {
-		if !v {
-			content.Defaults = append(content.Defaults, xlsxDefault{
-				Extension:   k,
-				ContentType: "image/" + k,
-			})
-		}
+	for extension, prefix := range imageTypes {
+		content.Defaults = append(content.Defaults, xlsxDefault{
+			Extension:   extension,
+			ContentType: prefix + extension,
+		})
 	}
 }
 
@@ -576,7 +573,7 @@ func (f *File) getPicture(row, col int, drawingXML, drawingRelationships string)
 		if err = nil; deTwoCellAnchor.From != nil && deTwoCellAnchor.Pic != nil {
 			if deTwoCellAnchor.From.Col == col && deTwoCellAnchor.From.Row == row {
 				drawRel = f.getDrawingRelationships(drawingRelationships, deTwoCellAnchor.Pic.BlipFill.Blip.Embed)
-				if _, ok = supportImageTypes[filepath.Ext(drawRel.Target)]; ok {
+				if _, ok = supportedImageTypes[filepath.Ext(drawRel.Target)]; ok {
 					ret = filepath.Base(drawRel.Target)
 					if buffer, _ := f.Pkg.Load(strings.Replace(drawRel.Target, "..", "xl", -1)); buffer != nil {
 						buf = buffer.([]byte)
@@ -605,7 +602,7 @@ func (f *File) getPictureFromWsDr(row, col int, drawingRelationships string, wsD
 			if anchor.From.Col == col && anchor.From.Row == row {
 				if drawRel = f.getDrawingRelationships(drawingRelationships,
 					anchor.Pic.BlipFill.Blip.Embed); drawRel != nil {
-					if _, ok = supportImageTypes[filepath.Ext(drawRel.Target)]; ok {
+					if _, ok = supportedImageTypes[filepath.Ext(drawRel.Target)]; ok {
 						ret = filepath.Base(drawRel.Target)
 						if buffer, _ := f.Pkg.Load(strings.Replace(drawRel.Target, "..", "xl", -1)); buffer != nil {
 							buf = buffer.([]byte)
diff --git a/picture_test.go b/picture_test.go
index fbbdf11..c548035 100644
--- a/picture_test.go
+++ b/picture_test.go
@@ -2,9 +2,11 @@ package excelize
 
 import (
 	"fmt"
+	"image"
 	_ "image/gif"
 	_ "image/jpeg"
 	_ "image/png"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -66,7 +68,7 @@ func TestAddPicture(t *testing.T) {
 	assert.NoError(t, f.AddPicture("Sheet1", "Q22", filepath.Join("test", "images", "excel.tif"), ""))
 
 	// Test write file to given path.
-	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestAddPicture.xlsx")))
+	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestAddPicture1.xlsx")))
 	assert.NoError(t, f.Close())
 }
 
@@ -89,7 +91,14 @@ func TestAddPictureErrors(t *testing.T) {
 
 	// Test add picture to worksheet with invalid file data.
 	err = f.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", ".jpg", make([]byte, 1))
-	assert.EqualError(t, err, "image: unknown format")
+	assert.EqualError(t, err, image.ErrFormat.Error())
+
+	// Test add picture with custom image decoder and encoder.
+	decode := func(r io.Reader) (image.Image, error) { return nil, nil }
+	decodeConfig := func(r io.Reader) (image.Config, error) { return image.Config{Height: 100, Width: 90}, nil }
+	image.RegisterFormat("emf", "", decode, decodeConfig)
+	assert.NoError(t, f.AddPicture("Sheet1", "Q1", filepath.Join("test", "images", "excel.emf"), ""))
+	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestAddPicture2.xlsx")))
 	assert.NoError(t, f.Close())
 }
 
diff --git a/sheet.go b/sheet.go
index 3986cd8..4665fd9 100644
--- a/sheet.go
+++ b/sheet.go
@@ -463,7 +463,7 @@ func (f *File) SetSheetBackground(sheet, picture string) error {
 	if _, err = os.Stat(picture); os.IsNotExist(err) {
 		return err
 	}
-	ext, ok := supportImageTypes[path.Ext(picture)]
+	ext, ok := supportedImageTypes[path.Ext(picture)]
 	if !ok {
 		return ErrImgExt
 	}
diff --git a/test/images/excel.emf b/test/images/excel.emf
new file mode 100644
index 0000000..9daa6de
--- /dev/null
+++ b/test/images/excel.emf
diff --git a/xmlDrawing.go b/xmlDrawing.go
index d6d6135..7d0b2df 100644
--- a/xmlDrawing.go
+++ b/xmlDrawing.go
@@ -118,7 +118,8 @@ const (
 	pivotTableVersion = 3
 )
 
-var supportImageTypes = map[string]string{".gif": ".gif", ".jpg": ".jpeg", ".jpeg": ".jpeg", ".png": ".png", ".tif": ".tiff", ".tiff": ".tiff"}
+// supportedImageTypes defined supported image types.
+var supportedImageTypes = map[string]string{".gif": ".gif", ".jpg": ".jpeg", ".jpeg": ".jpeg", ".png": ".png", ".tif": ".tiff", ".tiff": ".tiff", ".emf": ".emf"}
 
 // xlsxCNvPr directly maps the cNvPr (Non-Visual Drawing Properties). This
 // element specifies non-visual canvas properties. This allows for additional