Collinearity
Collinearity problems are most commonly found in architecture shots, where perspective causes objects to narrow, to “recede.”
You can use the Collinearity editing tool in Zoner Photo Studio to get rid of this problem fairly easily. After activating this tool, you drag out two vertical lines along the object's left and right edges, then use a toolbar button to confirm the edit.
Editing collinearity deforms an image somewhat, so an image that has been edited with this tool must be cropped to eliminate empty space at the edges. For minor edits, the Auto Crop option, which is on by default, should be sufficient.

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