Crop an image in Lightroom on mobile (Android)

Open a photo in the Detail view > select Crop & Rotate  .

Select the preferred tool to adjust your photo. 

Do one of the following for additional options:

• Aspect ratio: Select one of the available cropping aspect ratios.
• Locked: Select to crop without a preset aspect ratio.
• Straighten: Select to automatically straighten the photo.
• Rotate: Select to rotate the photo by 90 degrees.
• Flip H: Select to flip the photo horizontally.
• Flip V: Select to flip the photo vertically.
• Drag the cropping guide's edges and corners to change the crop's shape and size.
• You can drag the cropping wheel to crop the photo at a certain angle within -45 to 45 degrees. 
• Select within the cropping guide and drag it to reposition it.
  

Use the Upright menu to select automatic or manual Guided Upright perspective corrections.

Select the Auto Upright icon to automatically correct a photo's perspective. Choose the Guided Upright button to make perspective corrections manually by drawing guides directly on the photo.

Use the Transform slider to adjust the following:

• Distortion slider helps in adjusting the distortions often caused while capturing the photo
• Vertical slider helps in adjusting the vertical perspective, like straightening up or titling a vertical line  
• Horizontal slider helps in adjusting the horizontal lines
• Rotate slider helps in rotating the image in a clockwise or anticlockwise direction 
• Aspect slider helps define the aspect ratio of the entire image 
• Scale helps in zooming in or out of the image without affecting the aspect ratio
• X Offset helps in moving the image right or left 
• Y Offset helps in moving the image up or down

Check the Constrain Crop checkbox to restrict the Crop Overlay to the visible image area.