Masks
Download circuit.jpg from my website
Create a new flash document.
Create two layers name the bottom one background and the top one mask.
Select file import / import to stage (locate the image you just downloaded). Make sure the image is on the background layer.
On the mask layer select the oval tool and draw a circle about 80 pixels in the middle of the screen.
On frame 40 of the mask layer insert a blank keyframe.
Then on the background layer insert a frame at 80.
Next on frame 40 draw a large shape as below.
Then select frame 1 of the mask layer and open the properties panel. Next alter the Tween to shape to create a shape tween between the circle and the shape.
On the mask layer insert blank keyframe on frame 80 and then redraw the circle ensuring it is the same size as the previous one on the first frame. Then select frame 40 and in the properties panel change the tween to shape again.
Finally right click on the mask layer and select mask from the list.
Control test movie to see your animation.
Save the movie as mask.
Part 2
Using masks to create transitions.
Create a new flash document.
Create two layers called background and mask.
Select file import / import to stage (again locate the image you just downloaded for part 1). Make sure the image is on the background layer and lock this layer.
Select the rectangle tool and set the fill colour to black and the stroke colour to none.
On the mask layer, draw a large rectangle that is at least twice the height of the image.
Now select the selection tool and delete strips from the rectangle. To do this simply drag over the rectangle make a selection and press delete.
Your final shape should resemble below.
Select the entire shape and press F8 to convert it to a symbol, name it mymask and type a graphic.
On the background layer select frame 20 and press F5 to insert a frame.
Select the mask layer, frame 20 and press F6 to insert a keyframe.
On frame 20 of the mask layer place the solid black rectangle part of the mymask graphic so that it covers the image.
And on frame 1 ensure that the entire picture is visible.
Open the properties panel, select frame 1 of the mask layer and choose motion from the tween options.
Finally right click on the mask layer and select mask from the list.
Control / Test movie to see the animation.
Save your image as masktransition.
Exercise
See if you can expand this by including more images to make a slide show.