This would be simple and easy to batch convert your photo, please goto Irfanview download the latest version:
Step 1: Open IrfanView > Batch Conversion/Rename
- Right side select your photo and add in the batch
- Output directory for result files, please select which folder for the conversion output
- Select “Output format” and click “Options”
Step 3: JPEG select the Save quality, 100% is original size, here default resize is 80%
Step 4. Click “Start Batch” and wait it finish
Left is original size 905MB after reducing to 80% the size is 234MB, please check and make sure the quality is suitable for flushing photos and you accept before delete the original photo.