implement ignoring fully transparent sprites

src/com/gpl/rpg/atcontentstudio/ui/sprites/SpriteChooser.java

@@ -4,7 +4,6 @@ import java.awt.*;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.image.BufferedImage;
-import java.awt.image.WritableRaster;
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -15,6 +14,7 @@ import com.gpl.rpg.atcontentstudio.ATContentStudio;
 import com.gpl.rpg.atcontentstudio.model.Project;
 import com.gpl.rpg.atcontentstudio.model.sprites.Spritesheet;
 import com.gpl.rpg.atcontentstudio.model.sprites.Spritesheet.Category;
+import com.gpl.rpg.atcontentstudio.utils.SpriteUtils;
 
 
 public class SpriteChooser extends JDialog {
@@ -97,11 +97,14 @@ public class SpriteChooser extends JDialog {
 		Point nextFreeSlot = new Point(0, 0);
 
 		int i;
-		Image img;
+		BufferedImage img;
 		group = new ButtonGroup();
 		for (Spritesheet sheet : spritesheets) {
-			i = 0;
-			while ((img = sheet.getImage(i)) != null) {
+            i = -1;
+            while ((img = sheet.getImage(++i)) != null) {
+                if (SpriteUtils.checkIsImageEmpty(img)) {
+                    continue;
+                }
 				IconButton button = new IconButton(img, sheet.id, i);
 				group.add(button);
 				if (sheet.spriteWidth == STD_WIDTH && sheet.spriteHeight == STD_HEIGHT) {
@@ -150,7 +153,6 @@ public class SpriteChooser extends JDialog {
 					}
 					nextFreeSlot.setLocation(c.gridx, c.gridy);
 				}
-				i++;
 			}
 		}
 

src/com/gpl/rpg/atcontentstudio/utils/SpriteUtils.java

@@ -0,0 +1,34 @@
+package com.gpl.rpg.atcontentstudio.utils;
+
+import java.awt.image.BufferedImage;
+import java.awt.image.WritableRaster;
+
+public final class SpriteUtils {
+
+	/**
+	 * Check if the image is empty (transparent )
+	 *
+	 * @param img The image to check
+	 * @return true if the image is empty
+	 */
+	public static boolean checkIsImageEmpty(BufferedImage img) {
+		int width = img.getWidth(null);
+		int height = img.getHeight(null);
+		WritableRaster raster = img.getAlphaRaster();
+		if (raster == null) {
+			return false;
+		}
+		for (int x = 0; x < width; x++) {
+			for (int y = 0; y < height; y++) {
+				//get pixel alpha value
+				int alpha = raster.getSample(x, y, 0);
+				//if alpha is not 0 then the pixel is not transparent
+				if (alpha != 0) {
+					return false;
+				}
+			}
+		}
+		//no non-transparent pixel found
+		return true;
+	}
+}