internal/graphicscommand: browser screenshot/image dump support (#2269)

Closes #2265

imagedumper_mobile.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build android || ios || js
-// +build android ios js
+//go:build android || ios
+// +build android ios
 
 package ebiten
 

imagedumper_notmobile.go

@@ -12,14 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build !android && !ios && !js
-// +build !android,!ios,!js
+//go:build !android && !ios
+// +build !android,!ios
 
 package ebiten
 
 import (
+	"errors"
 	"fmt"
 	"os"
+	"syscall"
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/debug"
@@ -34,7 +36,7 @@ func availableFilename(prefix, postfix string) (string, error) {
 	name := fmt.Sprintf("%s%s%s", prefix, now.Format(datetimeFormat), postfix)
 	for i := 1; ; i++ {
 		if _, err := os.Stat(name); err != nil {
-			if os.IsNotExist(err) {
+			if os.IsNotExist(err) || errors.Is(err, syscall.ENOSYS) {
 				break
 			}
 			if !os.IsNotExist(err) {

internal/graphicscommand/image.go

@@ -15,11 +15,9 @@
 package graphicscommand
 
 import (
-	"fmt"
 	"image"
-	"os"
+	"io"
 	"sort"
-	"strings"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/affine"
 	"github.com/hajimehoshi/ebiten/v2/internal/debug"
@@ -190,25 +188,17 @@ func (i *Image) IsInvalidated() bool {
 	return i.image.IsInvalidated()
 }
 
-// Dump dumps the image to the specified path.
-// In the path, '*' is replaced with the image's ID.
+// dumpTo dumps the image to the specified writer.
 //
 // If blackbg is true, any alpha values in the dumped image will be 255.
 //
 // This is for testing usage.
-func (i *Image) Dump(graphicsDriver graphicsdriver.Graphics, path string, blackbg bool, rect image.Rectangle) error {
+func (i *Image) dumpTo(w io.Writer, graphicsDriver graphicsdriver.Graphics, blackbg bool, rect image.Rectangle) error {
 	// Screen image cannot be dumped.
 	if i.screen {
 		return nil
 	}
 
-	path = strings.ReplaceAll(path, "*", fmt.Sprintf("%d", i.id))
-	f, err := os.Create(path)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
 	pix := make([]byte, 4*i.width*i.height)
 	if err := i.ReadPixels(graphicsDriver, pix); err != nil {
 		return err
@@ -220,13 +210,14 @@ func (i *Image) Dump(graphicsDriver graphicsdriver.Graphics, path string, blackb
 		}
 	}
 
-	if err := png.Encode(f, (&image.RGBA{
+	if err := png.Encode(w, (&image.RGBA{
 		Pix:    pix,
 		Stride: 4 * i.width,
 		Rect:   image.Rect(0, 0, i.width, i.height),
 	}).SubImage(rect)); err != nil {
 		return err
 	}
+
 	return nil
 }
 

internal/graphicscommand/image_js.go

@@ -0,0 +1,58 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package graphicscommand
+
+import (
+	"bytes"
+	"image"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall/js"
+
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
+)
+
+func (i *Image) Dump(graphicsDriver graphicsdriver.Graphics, path string, blackbg bool, rect image.Rectangle) error {
+	// Screen image cannot be dumped.
+	if i.screen {
+		return nil
+	}
+
+	path = strings.ReplaceAll(path, "*", strconv.Itoa(i.id))
+	path = filepath.Base(path)
+
+	global := js.Global()
+
+	buf := &bytes.Buffer{}
+	if err := i.dumpTo(buf, graphicsDriver, blackbg, rect); err != nil {
+		return err
+	}
+
+	jsData := global.Get("Uint8Array").New(buf.Len())
+	js.CopyBytesToJS(jsData, buf.Bytes())
+
+	a := global.Get("document").Call("createElement", "a")
+	blob := global.Get("Blob").New(
+		[]interface{}{jsData},
+		map[string]interface{}{"type": "image/png"},
+	)
+	a.Set("href", global.Get("URL").Call("createObjectURL", blob))
+	a.Set("download", path)
+	a.Call("click")
+
+	return nil
+}
+

internal/graphicscommand/image_notjs.go

@@ -0,0 +1,47 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !js
+// +build !js
+
+package graphicscommand
+
+import (
+	"image"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
+)
+
+func (i *Image) Dump(graphicsDriver graphicsdriver.Graphics, path string, blackbg bool, rect image.Rectangle) error {
+	// Screen image cannot be dumped.
+	if i.screen {
+		return nil
+	}
+
+	path = strings.ReplaceAll(path, "*", strconv.Itoa(i.id))
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := i.dumpTo(f, graphicsDriver, blackbg, rect); err != nil {
+		return err
+	}
+
+	return nil
+}