[FFmpeg-user] color change when converting image to video

[Ronny Kurniawan]

 Hi everyone,I am a newbie to ffmpeg. I am currently trying to convert an image (which has a transparent background - alpha channel) to a 2 second video clip at 50fps. At the moment I did the following : 
ffmpeg -framerate 50 -loop 1 -i input_Image.png -t 2  -vcodec prores_ks -pix_fmt yuva444p10le -profile:v 4444 -alpha_bits 16 -an -y outputMovie.mov

This works but the video output has a slight color change and has a higher exposure for some reason. 
I tried this 
ffmpeg -framerate 50 -loop 1 -i input_Image.png  -t 2 -sws_flags spline+accurate_rnd+full_chroma_int -vf "colormatrix=bt470bg:bt709" -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 -vcodec prores_ks -pix_fmt yuva444p10le -profile:v 4444 -an -y outputMovie.mov


and it solved the color issue but then the alpha channel disappears. Would there be any suggestions on how I should resolve it.
Many thank's guys for your help.

Ronny