Crop JPG

Because JPEG does not support transparency, filling outer rotated margins with solid white or passport blue prevents black-box corner artifacts.

Yes, slightly. JPEG stores an approximation of the image rather than exact pixels, and saving again re-runs that approximation, so a small amount of detail is discarded even at quality 100. The loss is invisible once but compounds, so always crop from the original photo rather than from a file you already cropped, resized or compressed earlier. If you need several different crops of one photo, go back to the original each time.

Tools that advertise a lossless JPEG crop are copying the compressed data instead of re-encoding it, and JPEG stores that data in blocks — 8 pixels wide, or 16 when the file uses the usual 4:2:0 colour subsampling. A lossless crop can only cut on a block boundary, so it silently snaps your selection outward. PDFixel re-encodes, which means the crop lands exactly where you put it at the cost of one generation of JPEG loss.

Phone cameras usually save the sensor image in its native orientation and add an EXIF orientation flag telling viewers how to rotate it. Gallery apps honour that flag; some editors do not, which is why the same file can appear upright in one place and rotated in another. Use the straighten and rotation controls to correct it before cropping. Worth knowing either way: because the output is re-encoded from a canvas, the result carries no EXIF block at all, so camera model, timestamps and any GPS coordinates in the original are dropped.