Investigation of the surface modification of the p-type layer in GaN light-emitting diodes (LEDs) by exposure to a trifluoromethane plasma is reported. It is found that the plasma treatment reduces the conductivity of the p-GaN by several orders of magnitude, and when applied at room-temperature through a patterned mask, localized current channels into the active region of a p-i-n device are created. This provides a novel approach to laterally modulate the light emission from an LED over essentially planar areas. This technique allows the projection of high-resolution images from non-pixelated devices, and an example application of maskless pattern transfer with sub-micron features into photoresist is demonstrated.