Need help to upload images from sd card to iPad

I have a bit of problem with my SD card connection kit. Initially I was able to save lot of images from my laptop to SD card and upload it to IPAD using the SD Card connection kit. with no problem But for some reason it won't work anymore. I still can upload the image that I took direct from camera to SD card.

Is there any specific format that is used to save images so that it can be read by IPAD. I was using jpeg.

It just frustruating as I tried to change the size of the images and also change from 16bit to 8bit in sRGB with extension .jpeg but it still did not work.

If anyone know the trick I really appreciate it if you can let me know. The reason for me to download images to SD card from my laptop and portable hd is I need to resize all images and it is easier using camera raw software which let me resize lot of images in one go.