Create simply a reffet for your images with photoshop.
We start from with a jpg format image 'x-mas_ball', you can make use of it by clicking right on this ball and choose ' Save the picture as'.
Note that the height of the image is 448 pixels.

Open the image in Photoshop and save under the native format of Photoshop .psd
Right click on the layer 'Background' and choose 'Duplicate Layer'.

Name this layer as you want, in my example x-mas_ball.

Uncheck the eye beside the layer 'background' to work on the layer 'x-mas_ball', select that layer, it must be blue to be active.

In order to proceed with the Christmas ball cutout from its white background, I chose the tool 'magic wand'.
In some cases, you will have to use the pen tool to contour your object, I will return to this practice in a future tutorial.
Once the magic wand selected, in the options of this tool, enter '10 ' as 'Tolerance' and 'Contigous' must be checked.

Using the magic wand, select the first white zone (top left) , as example illustrated below.
Press 'Delete' or 'Del' to delete the white selected with the magic wand tool.

We see a gray and white checkerboard appears instead of white, this means 'transparency' in Photoshop.
Continue to select with the magic wand the white parts of the picture, one by one and delete, do not forget the part inside the attachment of the Christmas ball.

In under our image completely cut out.

We will now resize our work zone to accommodate the reflection .
Image > Canvas Size...

In the dialog box that opens:
-Make sure you are in units 'pixels' (yellow arrows).
-Click the top button (red arrow) because we want to expand our working area down.
-Check the 'relative' is checked (green arrow).
-Finally, enter the value of expanding the area of work desired: 448px (blue arrow).

You should end up with a work area similar to the illustration below.

Right click on the layer 'x-mas_ball' and choose 'Duplicate Layer'.

Name this duplicate layer 'shadow'.

Select the layer 'shadow' (it must be blue in the layers palette).
And to reverse the image Edit> Transform> Flip Vertical

The shadow layer is completely reversed.

Select the Move tool (shown below).
Confirming that the shadow layer is still selected.

Press the down keyboard arrow key move the ball layer 'shadow' down like in the illustration below.

Mask layer creation:
Make sure the layer 'shadow' is selected and click at the bottom of the Layers palette on the gray rectangle small icon with a white circle inside to create a mask.

Select the gradient tool.
If it does not appear, click and hold the bottom right corner of the paint bucket tool to bring up the selection palette 'paint bucket / gradient tool'.

Select the gradient tool options as illustrated below.

Move in click the gradient tool from point A to point B.
To draw a perfectly vertical line, hold down 'Shift' key while moving mouse clicked to point B.

The gradient is applied to the mask.
If you want to change it, select before (click on) the mask layer symbol in the'shadow' layer.

In the case of a reflection on a colored background.
It may be that you would like to make your gradient on a colored background as in the example of blue background below.

In this case, select the layer 'shadow' and select 'Multiply' property of the layer (see red arrow).

Returning to the starting example with transparent background.
Export in .png version to preserve transparency.
File> Save for Web & Devices ...

Make sure you are in PNG-24 and the box 'Transparency' is checked.
You can change the image size in 'Image Size ' box at the bottom of the dialog box.
Under the picture sample, weight of the picture image is displayed.
Finish by saving the image to the location of your choice.

Enjoy

Patrick