You should definitely switch to using Resize MyPix for Android as it is the best batch image Resizer on Android. Download links here for free version with ads and premium version no ads. Simply select the photos you need to resize and select the photo dimensions you need. Then Resize MyPix will automatically resize them, apply mild image sharpening to improve photo quality after the resizing process (can be disabled if you want though I don't know why since image quality is better), and it auto-rotates images to the correct orientation automatically. All images are then displayed in a grid for easy preview and you can even edit them if you need to (crop, flip, rotate, contrast, brightness, gamma, hue shift, grey-scale etc). Great easy to use interface definitely worth supporting the developer with paid version.