add hover animations to buttons

src/yugecin/opsudance/ui/ImagePosition.java

@@ -0,0 +1,41 @@
+/*
+ * opsu!dance - fork of opsu! with cursordance auto
+ * Copyright (C) 2018 yugecin
+ *
+ * opsu!dance is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * opsu!dance is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with opsu!dance.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package yugecin.opsudance.ui;
+
+import java.awt.Rectangle;
+
+import org.newdawn.slick.Image;
+
+public class ImagePosition extends Rectangle {
+	
+	private Image image;
+	
+	public ImagePosition(Image image) {
+		this.image = image;
+	}
+	
+	public boolean contains(int x, int y, float alphaThreshold) {
+		if (!super.contains(x, y)) {
+			return false;
+		}
+		final int ix = x - this.x;
+		final int iy = y - this.y;
+		return this.image.getAlphaAt(ix, iy) > alphaThreshold;
+	}
+
+}