Change TextAvatarService to TextAvatarUtil, color detection algorithm, Add fallback to username feature when FullName can't draw by default font.

src/main/scala/gitbucket/core/controller/AccountController.scala

@@ -21,13 +21,13 @@ import java.util.Date
 class AccountController extends AccountControllerBase
   with AccountService with RepositoryService with ActivityService with WikiService with LabelsService with SshKeyService
   with OneselfAuthenticator with UsersAuthenticator with GroupManagerAuthenticator with ReadableUsersAuthenticator
-  with AccessTokenService with WebHookService with RepositoryCreationService with TextAvatarService
+  with AccessTokenService with WebHookService with RepositoryCreationService
 
 
 trait AccountControllerBase extends AccountManagementControllerBase {
   self: AccountService with RepositoryService with ActivityService with WikiService with LabelsService with SshKeyService
     with OneselfAuthenticator with UsersAuthenticator with GroupManagerAuthenticator with ReadableUsersAuthenticator
-    with AccessTokenService with WebHookService with RepositoryCreationService with TextAvatarService =>
+    with AccessTokenService with WebHookService with RepositoryCreationService =>
 
   case class AccountNewForm(userName: String, password: String, fullName: String, mailAddress: String,
                             description: Option[String], url: Option[String], fileId: Option[String])
@@ -151,13 +151,12 @@ trait AccountControllerBase extends AccountManagementControllerBase {
   get("/:userName/_avatar"){
     val userName = params("userName")
     getAccountByUserName(userName).map{ account =>
+      response.setDateHeader("Last-Modified", account.updatedDate.getTime)
       account.image.map{ image =>
-        response.setDateHeader("Last-Modified", account.updatedDate.getTime)
         RawData(FileUtil.getMimeType(image), new java.io.File(getUserUploadDir(userName), image))
       }.getOrElse{
         contentType = "image/png"
-        response.setDateHeader("Last-Modified", new Date(0).getTime())
-        textAvatar(account.fullName)
+        TextAvatarUtil.textAvatar(account.fullName).getOrElse(Thread.currentThread.getContextClassLoader.getResourceAsStream("noimage.png"))
       }
     }.getOrElse{
       NotFound()

src/main/scala/gitbucket/core/service/TextAvatarService.scala

@@ -1,49 +0,0 @@
-package gitbucket.core.service
-
-import java.io.ByteArrayOutputStream
-import java.awt.image.BufferedImage
-import javax.imageio.ImageIO
-import java.awt.{Color, Font, RenderingHints}
-import java.awt.font.{FontRenderContext, TextLayout}
-import gitbucket.core.util.StringUtil
-
-trait TextAvatarService {
-  def textAvatar(nameText: String): Array[Byte] = {
-    val drawText = nameText.substring(0, 1)
-    val md5 = StringUtil.md5(nameText)
-    val hashedInt = Integer.parseInt(md5.substring(0, 2), 16)
-
-    val h = hashedInt / 256f
-    val bgColor = Color.getHSBColor(h, 1f, 1f)
-    val fgColor = Color.getHSBColor(h + 0.5f, 1f, 0.8f)
-
-    val size = (200, 200)
-    val canvas = new BufferedImage(size._1, size._2, BufferedImage.TYPE_INT_ARGB)
-    val g = canvas.createGraphics()
-
-    g.setColor(new Color(0, 0, 0, 0))
-    g.fillRect(0, 0, canvas.getWidth, canvas.getHeight)
-    g.setColor(bgColor)
-    g.fillRoundRect(0, 0, canvas.getWidth, canvas.getHeight, 60, 60)
-
-    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
-
-    g.setColor(fgColor)
-    val font = new Font("SansSerif", Font.PLAIN, 180)
-    val context = g.getFontRenderContext
-    val txt = new TextLayout(drawText, font, context)
-    val bounds = txt.getBounds
-
-    val x: Int = ((size._1 - bounds.getWidth) / 2 - bounds.getX).toInt
-    val y: Int = ((size._2 - bounds.getHeight) / 2 - bounds.getY).toInt
-
-    g.setFont(font)
-    g.drawString(drawText, x, y)
-
-    g.dispose()
-
-    val stream = new ByteArrayOutputStream
-    ImageIO.write(canvas, "png", stream)
-    stream.toByteArray
-  }
-}

src/main/scala/gitbucket/core/util/TextAvatarUtil.scala

@@ -0,0 +1,72 @@
+package gitbucket.core.util
+
+import java.io.ByteArrayOutputStream
+import java.awt.image.BufferedImage
+import javax.imageio.ImageIO
+import java.awt.{Color, Font, RenderingHints}
+import java.awt.font.{FontRenderContext, TextLayout}
+
+object TextAvatarUtil {
+  // https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
+  private def relativeLuminance(c: Color): Double = {
+    val rgb = Seq(c.getRed, c.getGreen, c.getBlue).map{_/255.0}.map{x => if (x <= 0.03928) x / 12.92 else math.pow((x + 0.055) / 1.055, 2.4)}
+    0.2126 * rgb(0) + 0.7152 * rgb(1) + 0.0722 * rgb(2)
+  }
+
+  // https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
+  private def contrastRatio(c1: Color, c2: Color): Double = {
+    val l1 = relativeLuminance(c1)
+    val l2 = relativeLuminance(c2)
+    if (l1 > l2) (l1 + 0.05) / (l2 + 0.05) else (l2 + 0.05) / (l1 + 0.05)
+  }
+
+  private def goodContrastColor(base: Color, c1: Color, c2: Color): Color = {
+    if (contrastRatio(base, c1) > contrastRatio(base, c2)) c1 else c2
+  }
+
+  private def textImage(w: Int, h: Int, drawText: String, font: Font, fontSize: Int, bgColor: Color, fgColor: Color): Array[Byte] = {
+    val canvas = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB)
+    val g = canvas.createGraphics()
+
+    g.setColor(new Color(0, 0, 0, 0))
+    g.fillRect(0, 0, w, h)
+    g.setColor(bgColor)
+    g.fillRoundRect(0, 0, w, h, 60, 60)
+
+    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
+
+    g.setColor(fgColor)
+    val context = g.getFontRenderContext
+    val txt = new TextLayout(drawText, font, context)
+    val bounds = txt.getBounds
+
+    val x: Int = ((w - bounds.getWidth) / 2 - bounds.getX).toInt
+    val y: Int = ((h - bounds.getHeight) / 2 - bounds.getY).toInt
+
+    g.setFont(font)
+    g.drawString(drawText, x, y)
+
+    g.dispose()
+
+    val stream = new ByteArrayOutputStream
+    ImageIO.write(canvas, "png", stream)
+    stream.toByteArray
+  }
+
+  def textAvatar(nameText: String): Option[Array[Byte]] = {
+    val drawText = nameText.substring(0, 1)
+    val md5 = StringUtil.md5(nameText)
+    val hashedInt = Integer.parseInt(md5.substring(0, 2), 16)
+
+    val bgHue = hashedInt / 256f
+    val bgSaturation = 0.68f
+    val bgBlightness = 0.73f
+    val bgColor = Color.getHSBColor(bgHue, bgSaturation, bgBlightness)
+    val fgColor = goodContrastColor(bgColor, Color.BLACK, Color.WHITE)
+
+    val size = (200, 200)
+    val fontSize = 180
+    val font = new Font(Font.SANS_SERIF, Font.PLAIN, fontSize)
+    if (font.canDisplayUpTo(drawText) == -1) Some(textImage(size._1, size._2, drawText, font, fontSize, bgColor, fgColor)) else None
+  }
+}