how to fade two images with ffmpeg

Question

I have two images and I want to create a simple fading transition between them.

I also want the final output to be a sequence of images rather than a video? So if

Answer 1

Try this:

ffmpeg \
-loop 1 -t 3 -i input1.png \
-loop 1 -t 3 -i input2.png \
-loop 1 -t 3 -i input3.png \
-loop 1 -t 3 -i input4.png \
-loop 1 -t 3 -i input5.png \
-filter_complex \
"[1:v][0:v]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v0]; \
 [2:v][1:v]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v1]; \
 [3:v][2:v]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v2]; \
 [4:v][3:v]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v3]; \
 [v0][v1][v2][v3]concat=n=4:v=1:a=0[v]"
-map "[v]" out.mp4

Haven't tried with images, but you could try -t 12 frames_%04d.png at the end or whatever.