add: basic shape for API

.gitignore

@@ -12,3 +12,4 @@
 
 # Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736
 .glide/
+.idea/workspace.xml

.idea/captcha.iml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+  <component name="Go" enabled="true" />
+  <component name="NewModuleRootManager">
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/captcha.iml" filepath="$PROJECT_DIR$/.idea/captcha.iml" />
+    </modules>
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

captcha.go

@@ -0,0 +1,59 @@
+package captcha
+
+import (
+	"io"
+	"image/color"
+	"image"
+	"image/png"
+	"math/rand"
+	"time"
+)
+
+const charPreset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+
+type Options struct {
+	BackgroundColor color.RGBA
+	CharPreset string
+	TxtLength int
+}
+
+func newDefaultOption() *Options {
+	return &Options{
+		CharPreset: charPreset,
+		TxtLength: 4,
+	}
+}
+
+type Option func(*Options)
+
+type Data struct {
+	Text string
+
+	img *image.NRGBA
+}
+
+func (data *Data) WriteTo(w io.Writer) error {
+	return png.Encode(w, data.img)
+}
+
+func New(width int, height int, option... Option) *Data {
+	options := newDefaultOption()
+	for _, setOption := range option {
+		setOption(options)
+	}
+
+	text := randomText(options)
+	img := image.NewNRGBA(image.Rect(0, 0, width, height))
+
+	return &Data{Text: text, img: img}
+}
+
+func randomText(opts *Options) (text string) {
+	n := len(opts.CharPreset)
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+	for i :=0; i < opts.TxtLength; i++ {
+		text += string(opts.CharPreset[r.Intn(n)])
+	}
+
+	return text
+}

fonts/LICENSE.md

@@ -0,0 +1,2 @@
+license: free  
+website: http://www.moorstation.org/typoasis/designers/gemnew/home.htm