Image Editing and Manipulation
Selections, layers and adjustments
Editing starts with selecting the area to change. Marquee tools select rectangles and ellipses; lasso and freehand tools trace irregular shapes; magic wand and quick-selection tools find similar colour or edges. Feathering softens selection edges; tolerance controls how closely colours must match. Layers, masks, and adjustment layers allow non-destructive work: a mask hides rather than deletes, and an adjustment layer can be revised or removed later.
Geometry and tone
Cropping removes pixels; resizing changes pixel dimensions (resampling) or physical print size; canvas size adds or removes space without scaling content. Rotate, flip, skew, perspective, and free transform correct orientation and shape. Brightness, contrast, levels, curves, hue/saturation, and colour balance adjust tone and colour. Filters blur, sharpen, stylise, or add texture. Retouching tools such as clone stamp and healing brush remove blemishes. History or undo steps allow reversal, but only within the current session and up to the configured limit.
Traps: upscaling a small image and expecting new detail; sharpening before resizing; cropping after saving over the original; using destructive filters when adjustment layers would do; forgetting that a selection limits every edit that follows.
Worked example: for a photo needing straightening, colour correction, resizing, and export, work in this order: straighten and crop, correct tone and colour, retouch locally, resize to final pixels, sharpen, then export a copy. Rule of thumb: geometry first, global adjustments next, local retouching, then output sharpening.