完善剪裁窗口颜色拾取功能，工具栏图标同步更新

gallery/src/main/java/cc/winboll/studio/gallery/CropActivity.java

@@ -127,6 +127,7 @@ public class CropActivity extends AppCompatActivity {
             public void onColorPicked(int color) {
                 int pickX = cropCanvasView.getLastPickImageX();
                 int pickY = cropCanvasView.getLastPickImageY();
+                colorView.setBackgroundColor(color);
                 Toast.makeText(CropActivity.this, 
                     "颜色已拾取: #" + String.format("%06X", color & 0xFFFFFF) + 
                     " (" + pickX + "," + pickY + ")", 

gallery/src/main/java/cc/winboll/studio/gallery/CropCanvasView.java

@@ -528,10 +528,19 @@ public class CropCanvasView extends View {
                 return true;
             }
             if (event.getAction() == MotionEvent.ACTION_UP) {
-                if (previewColor != 0 && previewColor != Color.TRANSPARENT) {
-                    backgroundColor = previewColor;
+                if (canvasBounds.contains(x, y)) {
+                    int pickedColor;
+                    float imgX = screenToImageX(x);
+                    float imgY = screenToImageY(y);
+                    if (imageBounds.contains(imgX, imgY)) {
+                        int colorAtPoint = getImageColorAt(x, y);
+                        pickedColor = colorAtPoint;
+                        backgroundColor = colorAtPoint;
+                    } else {
+                        pickedColor = backgroundColor;
+                    }
                     if (colorPickedListener != null) {
-                        colorPickedListener.onColorPicked(backgroundColor);
+                        colorPickedListener.onColorPicked(pickedColor);
                     }
                 }
                 if (colorPickEndListener != null) {