image: add an example that shows how to get the metadata of an image

This is a simple but everyday use case in image libraries. Currently,
there is one example in this library and it is lengthy and involved.

This PR will be imported into Gerrit with the title and first
comment (this text) used to generate the subject and body of
the Gerrit change.

Change-Id: Idca527d97c095af88755446e1548fa2b8ace7eb0
GitHub-Last-Rev: f5743c8ef337a8b7a5126db21d784593f4f53c8a
GitHub-Pull-Request: golang/go#25616
Reviewed-on: https://go-review.googlesource.com/114939
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/image/decode_example_test.go b/src/image/decode_example_test.go
index 81fa0378e171ea4bccad85fd0e2a50b31e4fac67..526c03f3c1a78b02ac77a56038ef673fe1a368ed 100644 (file)
--- a/src/image/decode_example_test.go
+++ b/src/image/decode_example_test.go
@@ -21,6 +21,15 @@ import (
        _ "image/jpeg"
 )
 
+func Example_decodeConfig() {
+       reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
+       config, format, err := image.DecodeConfig(reader)
+       if err != nil {
+               log.Fatal(err)
+       }
+       fmt.Println("Width:", config.Width, "Height:", config.Height, "Format:", format)
+}
+
 func Example() {
        // Decode the JPEG data. If reading from file, create a reader with
        //