diff --git a/README.md b/README.md
index d9c25c0..67be8cb 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@ $ go get github.com/kaneshin/pigeon
 # Default Detection is LabelDetection.
 $ pigeon assets/lenna.jpg
 $ pigeon -face gs://bucket_name/lenna.jpg
+$ pigeon -label https://httpbin.org/image/jpeg
 ```
 
 ![pigeon-cmd](https://raw.githubusercontent.com/kaneshin/pigeon/master/assets/pigeon-cmd.gif)
@@ -87,14 +88,16 @@ func main() {
 	// "GOOGLE_APPLICATION_CREDENTIALS" if pass empty string to argument.
 	// creds := credentials.NewApplicationCredentials("")
 
-	client, err := pigeon.New(creds)
+	config := NewConfig().WithCredentials(creds)
+
+	client, err := pigeon.New(config)
 	if err != nil {
 		panic(err)
 	}
 
 	// To call multiple image annotation requests.
 	feature := pigeon.NewFeature(pigeon.LabelDetection)
-	batch, err := pigeon.NewBatchAnnotateImageRequest([]string{"lenna.jpg"}, feature)
+	batch, err := client.NewBatchAnnotateImageRequest([]string{"lenna.jpg"}, feature)
 	if err != nil {
 		panic(err)
 	}
@@ -191,7 +194,7 @@ if err != nil {
 
 ```go
 // To call multiple image annotation requests.
-batch, err := pigeon.NewBatchAnnotateImageRequest(list, features()...)
+batch, err := client.NewBatchAnnotateImageRequest(list, features()...)
 if err != nil {
 	panic(err)
 }
diff --git a/client.go b/client.go
index f65a649..09e6bf3 100644
--- a/client.go
+++ b/client.go
@@ -1,8 +1,12 @@
 package pigeon
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
 
 	"golang.org/x/net/context"
 	"golang.org/x/oauth2/google"
@@ -12,15 +16,35 @@ import (
 )
 
 type (
-	// Client is
+	// A Client provides cloud vision service.
 	Client struct {
+		// The context object to use when signing requests.
+		// Defaults to `context.Background()`.
+		// context context.Context
+
+		// The Config provides service configuration for service clients.
+		config *Config
+
+		// The service object.
 		service *vision.Service
 	}
 )
 
 // New returns a pointer to a new Client object.
-func New(c *credentials.Credentials) (*Client, error) {
-	creds, err := c.Get()
+func New(c *Config) (*Client, error) {
+	if c == nil {
+		// Sets a configuration if passed nil value.
+		c = NewConfig()
+	}
+
+	// TODO: Running on GAE.
+
+	if c.Credentials == nil {
+		// Sets application credentials by defaults.
+		c.Credentials = credentials.NewApplicationCredentials("")
+	}
+
+	creds, err := c.Credentials.Get()
 	if err != nil {
 		return nil, err
 	}
@@ -38,6 +62,7 @@ func New(c *credentials.Credentials) (*Client, error) {
 	}
 
 	return &Client{
+		config:  c,
 		service: srv,
 	}, nil
 }
@@ -46,3 +71,101 @@ func New(c *credentials.Credentials) (*Client, error) {
 func (c Client) ImagesService() *vision.ImagesService {
 	return c.service.Images
 }
+
+// NewBatchAnnotateImageRequest returns a pointer to a new vision's BatchAnnotateImagesRequest.
+func (c Client) NewBatchAnnotateImageRequest(list []string, features ...*vision.Feature) (*vision.BatchAnnotateImagesRequest, error) {
+	batch := &vision.BatchAnnotateImagesRequest{}
+	batch.Requests = []*vision.AnnotateImageRequest{}
+	for _, v := range list {
+		req, err := c.NewAnnotateImageRequest(v, features...)
+		if err != nil {
+			return nil, err
+		}
+		batch.Requests = append(batch.Requests, req)
+	}
+	return batch, nil
+}
+
+// NewAnnotateImageRequest returns a pointer to a new vision's AnnotateImagesRequest.
+func (c Client) NewAnnotateImageRequest(v interface{}, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
+	switch v.(type) {
+	case []byte:
+		// base64
+		return NewAnnotateImageContentRequest(v.([]byte), features...)
+	case string:
+		u, err := url.Parse(v.(string))
+		if err != nil {
+			return nil, err
+		}
+		switch u.Scheme {
+		case "gs":
+			// GcsImageUri: Google Cloud Storage image URI. It must be in the
+			// following form:
+			// "gs://bucket_name/object_name". For more
+			return NewAnnotateImageSourceRequest(u.String(), features...)
+		case "http", "https":
+			httpClient := c.config.HTTPClient
+			if httpClient == nil {
+				httpClient = http.DefaultClient
+			}
+			resp, err := httpClient.Get(u.String())
+			if err != nil {
+				return nil, err
+			}
+			defer resp.Body.Close()
+			if resp.StatusCode >= http.StatusBadRequest {
+				return nil, http.ErrMissingFile
+			}
+			body, err := ioutil.ReadAll(resp.Body)
+			if err != nil {
+				return nil, err
+			}
+			return c.NewAnnotateImageRequest(body, features...)
+		}
+		// filepath
+		b, err := ioutil.ReadFile(u.String())
+		if err != nil {
+			return nil, err
+		}
+		return c.NewAnnotateImageRequest(b, features...)
+	}
+	return &vision.AnnotateImageRequest{}, nil
+}
+
+// NewAnnotateImageContentRequest returns a pointer to a new vision's AnnotateImagesRequest.
+func NewAnnotateImageContentRequest(body []byte, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
+	req := &vision.AnnotateImageRequest{
+		Image:    NewAnnotateImageContent(body),
+		Features: features,
+	}
+	return req, nil
+}
+
+// NewAnnotateImageSourceRequest returns a pointer to a new vision's AnnotateImagesRequest.
+func NewAnnotateImageSourceRequest(source string, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
+	req := &vision.AnnotateImageRequest{
+		Image:    NewAnnotateImageSource(source),
+		Features: features,
+	}
+	return req, nil
+}
+
+// NewAnnotateImageContent returns a pointer to a new vision's Image.
+// It's contained image content, represented as a stream of bytes.
+func NewAnnotateImageContent(body []byte) *vision.Image {
+	return &vision.Image{
+		// Content: Image content, represented as a stream of bytes.
+		Content: base64.StdEncoding.EncodeToString(body),
+	}
+}
+
+// NewAnnotateImageSource returns a pointer to a new vision's Image.
+// It's contained external image source (i.e. Google Cloud Storage image
+// location).
+func NewAnnotateImageSource(source string) *vision.Image {
+	return &vision.Image{
+		Source: &vision.ImageSource{
+			GcsImageUri: source,
+		},
+	}
+}
diff --git a/client_test.go b/client_test.go
index d4d201b..495f11e 100644
--- a/client_test.go
+++ b/client_test.go
@@ -4,8 +4,8 @@ import (
 	"os"
 	"testing"
 
-	"github.com/kaneshin/pigeon/credentials"
 	"github.com/stretchr/testify/assert"
+	vision "google.golang.org/api/vision/v1"
 )
 
 func TestClient(t *testing.T) {
@@ -13,16 +13,62 @@ func TestClient(t *testing.T) {
 
 	assert := assert.New(t)
 
-	creds := credentials.NewApplicationCredentials("")
-	client, err := New(creds)
+	conf := NewConfig()
+	client, err := New(conf)
 	assert.Nil(client)
 	assert.Error(err)
 
 	os.Setenv("GOOGLE_APPLICATION_CREDENTIALS", "credentials/example.json")
-	creds = credentials.NewApplicationCredentials("")
-	client, err = New(creds)
+	conf = NewConfig()
+	client, err = New(conf)
 	assert.NotNil(client)
 	assert.NoError(err)
 	assert.NotNil(client.service)
 	assert.NotNil(client.ImagesService())
 }
+
+func TestNewAnnotateImageRequest(t *testing.T) {
+	assert := assert.New(t)
+
+	var (
+		req *vision.AnnotateImageRequest
+		err error
+	)
+	const (
+		gcsImageURI      = "gs://bucket/sample.png"
+		fp               = "assets/lenna.jpg"
+		imageURI         = "https://httpbin.org/image/jpeg"
+		imageURINoExists = "https://httpbin.org/image/jpeg/none"
+	)
+	features := NewFeature(LabelDetection)
+	client, err := New(nil)
+	assert.NoError(err)
+
+	// GCS
+	req, err = client.NewAnnotateImageRequest(gcsImageURI, features)
+	assert.NoError(err)
+	if assert.NotNil(req) {
+		assert.Equal("", req.Image.Content)
+		assert.Equal(gcsImageURI, req.Image.Source.GcsImageUri)
+	}
+
+	// Filepath
+	req, err = client.NewAnnotateImageRequest(fp, features)
+	assert.NoError(err)
+	if assert.NotNil(req) {
+		assert.NotEqual("", req.Image.Content)
+		assert.Nil(req.Image.Source)
+	}
+
+	// Image URI
+	req, err = client.NewAnnotateImageRequest(imageURI, features)
+	assert.NoError(err)
+	if assert.NotNil(req) {
+		assert.NotEqual("", req.Image.Content)
+		assert.Nil(req.Image.Source)
+	}
+
+	req, err = client.NewAnnotateImageRequest(imageURINoExists, features)
+	assert.Error(err)
+	assert.Nil(req)
+}
diff --git a/config.go b/config.go
new file mode 100644
index 0000000..2ad0f2f
--- /dev/null
+++ b/config.go
@@ -0,0 +1,40 @@
+package pigeon
+
+import (
+	"net/http"
+
+	"github.com/kaneshin/pigeon/credentials"
+)
+
+type (
+	// A Config provides service configuration for service clients. By default,
+	// all clients will use the {defaults.DefaultConfig} structure.
+	Config struct {
+		// The credentials object to use when signing requests.
+		// Defaults to application credentials file.
+		Credentials *credentials.Credentials
+
+		// The HTTP client to use when sending requests.
+		// Defaults to `http.DefaultClient`.
+		HTTPClient *http.Client
+	}
+)
+
+// NewConfig returns a pointer of new Config objects.
+func NewConfig() *Config {
+	return &Config{}
+}
+
+// WithCredentials sets a config Credentials value returning a Config pointer
+// for chaining.
+func (c *Config) WithCredentials(creds *credentials.Credentials) *Config {
+	c.Credentials = creds
+	return c
+}
+
+// WithHTTPClient sets a config HTTPClient value returning a Config pointer
+// for chaining.
+func (c *Config) WithHTTPClient(client *http.Client) *Config {
+	c.HTTPClient = client
+	return c
+}
diff --git a/config_test.go b/config_test.go
new file mode 100644
index 0000000..cf80a72
--- /dev/null
+++ b/config_test.go
@@ -0,0 +1,25 @@
+package pigeon
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/kaneshin/pigeon/credentials"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConfig(t *testing.T) {
+	assert := assert.New(t)
+
+	conf := NewConfig()
+	assert.NotNil(conf)
+	assert.Nil(conf.Credentials)
+	assert.Nil(conf.HTTPClient)
+
+	creds := credentials.NewApplicationCredentials("")
+	client := http.DefaultClient
+	conf.WithCredentials(creds).
+		WithHTTPClient(client)
+	assert.NotNil(conf.Credentials)
+	assert.NotNil(conf.HTTPClient)
+}
diff --git a/request.go b/request.go
deleted file mode 100644
index 509f802..0000000
--- a/request.go
+++ /dev/null
@@ -1,89 +0,0 @@
-package pigeon
-
-import (
-	"encoding/base64"
-	"io/ioutil"
-	"strings"
-
-	vision "google.golang.org/api/vision/v1"
-)
-
-var (
-	emptyAnnotateImageRequest = &vision.AnnotateImageRequest{}
-)
-
-// NewAnnotateImageContent returns a pointer to a new vision's Image.
-// It's contained image content, represented as a stream of bytes.
-func NewAnnotateImageContent(body []byte) *vision.Image {
-	return &vision.Image{
-		// Content: Image content, represented as a stream of bytes.
-		Content: base64.StdEncoding.EncodeToString(body),
-	}
-}
-
-// NewAnnotateImageSource returns a pointer to a new vision's Image.
-// It's contained external image source (i.e. Google Cloud Storage image
-// location).
-func NewAnnotateImageSource(source string) *vision.Image {
-	return &vision.Image{
-		Source: &vision.ImageSource{
-			GcsImageUri: source,
-		},
-	}
-}
-
-// NewBatchAnnotateImageRequest returns a pointer to a new vision's BatchAnnotateImagesRequest.
-func NewBatchAnnotateImageRequest(list []string, features ...*vision.Feature) (*vision.BatchAnnotateImagesRequest, error) {
-	batch := &vision.BatchAnnotateImagesRequest{}
-	batch.Requests = []*vision.AnnotateImageRequest{}
-	for _, v := range list {
-		req, err := NewAnnotateImageRequest(v, features...)
-		if err != nil {
-			return nil, err
-		}
-		batch.Requests = append(batch.Requests, req)
-	}
-	return batch, nil
-}
-
-// NewAnnotateImageRequest returns a pointer to a new vision's AnnotateImagesRequest.
-func NewAnnotateImageRequest(v interface{}, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
-	switch v.(type) {
-	case []byte:
-		// base64
-		return NewAnnotateImageContentRequest(v.([]byte), features...)
-	case string:
-		str := v.(string)
-		if strings.HasPrefix(str, "gs://") {
-			// GcsImageUri: Google Cloud Storage image URI. It must be in the
-			// following form:
-			// "gs://bucket_name/object_name". For more
-			return NewAnnotateImageSourceRequest(str, features...)
-		}
-		// filepath
-		b, err := ioutil.ReadFile(str)
-		if err != nil {
-			return nil, err
-		}
-		return NewAnnotateImageRequest(b, features...)
-	}
-	return emptyAnnotateImageRequest, nil
-}
-
-// NewAnnotateImageContentRequest returns a pointer to a new vision's AnnotateImagesRequest.
-func NewAnnotateImageContentRequest(body []byte, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
-	req := &vision.AnnotateImageRequest{
-		Image:    NewAnnotateImageContent(body),
-		Features: features,
-	}
-	return req, nil
-}
-
-// NewAnnotateImageSourceRequest returns a pointer to a new vision's AnnotateImagesRequest.
-func NewAnnotateImageSourceRequest(source string, features ...*vision.Feature) (*vision.AnnotateImageRequest, error) {
-	req := &vision.AnnotateImageRequest{
-		Image:    NewAnnotateImageSource(source),
-		Features: features,
-	}
-	return req, nil
-}
diff --git a/request_test.go b/request_test.go
deleted file mode 100644
index bbc3551..0000000
--- a/request_test.go
+++ /dev/null
@@ -1 +0,0 @@
-package pigeon
diff --git a/tools/cmd/pigeon-app/main.go b/tools/cmd/pigeon-app/main.go
index c39006f..f7c23e8 100644
--- a/tools/cmd/pigeon-app/main.go
+++ b/tools/cmd/pigeon-app/main.go
@@ -12,7 +12,6 @@ import (
 	vision "google.golang.org/api/vision/v1"
 
 	"github.com/kaneshin/pigeon"
-	"github.com/kaneshin/pigeon/credentials"
 	"github.com/kaneshin/pigeon/tools/cmd"
 )
 
@@ -24,8 +23,7 @@ func main() {
 	detects := cmd.DetectionsParse(flag.Args()[:])
 
 	// Initialize vision service by a credentials json.
-	c := credentials.NewApplicationCredentials("")
-	client, err := pigeon.New(c)
+	client, err := pigeon.New(nil)
 	if err != nil {
 		panic(err)
 	}
diff --git a/tools/cmd/pigeon/main.go b/tools/cmd/pigeon/main.go
index d7a3537..b8dcd59 100644
--- a/tools/cmd/pigeon/main.go
+++ b/tools/cmd/pigeon/main.go
@@ -7,7 +7,6 @@ import (
 	"os"
 
 	"github.com/kaneshin/pigeon"
-	"github.com/kaneshin/pigeon/credentials"
 	"github.com/kaneshin/pigeon/tools/cmd"
 )
 
@@ -22,14 +21,13 @@ func main() {
 	}
 
 	// Initialize vision service by a credentials json.
-	c := credentials.NewApplicationCredentials("")
-	client, err := pigeon.New(c)
+	client, err := pigeon.New(nil)
 	if err != nil {
 		log.Fatalf("Unable to retrieve vision service: %v\n", err)
 	}
 
 	// To call multiple image annotation requests.
-	batch, err := pigeon.NewBatchAnnotateImageRequest(detects.Args(), detects.Features()...)
+	batch, err := client.NewBatchAnnotateImageRequest(detects.Args(), detects.Features()...)
 	if err != nil {
 		log.Fatalf("Unable to retrieve image request: %v\n", err)
 	}