How can I make a list animation of images that fade in and out?

Question

I'm not sure how to get a "fade in" effect.

Answer 1

Start from understanding and setting up an transition functions sequence:

Plot[Evaluate@Table[(1 + Tanh[tr (x - dt n)])/2, {n, 1, Length[imgs], 1}], {x, 0, 
  dt (Length[imgs] + 1)}, PlotStyle -> Thick]

Set your images as a list:

Set 2 main parameters of your animation:

tr = 1;(* transition speed *)
dt = 4;(* display time *)

Finally use interactive interface

Animate[Overlay[Table[SetAlphaChannel[imgs[[n]], (1 + Tanh[tr (x - dt n)])/2], {n, 1, 
    Length[imgs], 1}]], {x, 0, dt (Length[imgs] + 1), 
  ImageSize -> Small}, AnimationRate -> 2]

Or make a table and export as an .GIF image

gift = Table[Overlay[Table[SetAlphaChannel[imgs[[n]], (1 + Tanh[tr (x - dt n)])/2], {n,
       1, Length[imgs], 1}]], {x, 0, dt (Length[imgs] + 1), 
    dt (Length[imgs] + 1)/50}];

Export["MyVacationSlideShow.gif", gift]

Answer 2

Vitaliy has a great answer, however I wanted to try my hand at this to get something a bit smoother in action by using Dynamics...

images = ImageResize[#, 500] & /@ ExampleData /@ ExampleData["TestImage"][[1 ;; 7]];
i = 1;
Dynamic[
    Which[Or @@ Thread[i == Range[Length[images]]], Pause[2]; i += .01, 
      i < Length[images] - 1, i += .01, 
      True, i = 1]; fade = Mod[i, 1];
 ImageCompose[images[[IntegerPart[i]]], {images[[IntegerPart[i] + 1]], fade}]
]

This works, but can someone please tell me why I can't substitute IntegerQ[i] for Or @@ Thread[i == Range[Length[images]]]?