"Few come to Edinburgh in August for the art but this year they should. The line-up for the official Art Festival is impressive and, happily, rich in painters. Foremost among them is Peter Doig, whose semi-retrospective No Foreign Landsis the main event at the Scottish National Gallery (until 3 November).

Doig was born in Edinburgh in 1959 and is being claimed as 'one of us'. That he left the country as a baby should not stand in the way here; we need painters like this. For too long now, perceptions of art in Scotland have been skewed by the consistent success of Glasgow artists in the Turner Prize. As Doig himself has said, the influential art prize should not be the Turner but the John Moores, the annual award for painting that Doig won in 1993. Ken Currie, exhibiting new work this summer at the Scottish National Portrait Gallery (until 22 September), has been outspoken about painting's apparent lack of status in the current art school system but nevertheless it is painters in whom the National Galleries of Scotland have invested their efforts this summer.

And quite right too. The Peter Doig show is a remarkable thing. I defy any art student to view this exhibition and conclude that painting is over; that it has no relevance today. Doig's work, which treads the borders of realities, carrying the viewer through landscapes real and imagined, is vital stuff. This exhibition shows work created since he returned in 2000 to Trinidad where he had lived as a child. Currie suggested recently that an artist will spend the years between 20 and 40 finding his voice. Doig was 40 when he went back to Trinidad, so perhaps we can view this show as a study of his maturity.

The work, rich in imagination and technique, is certainly assured. The subject matter, often an amalgam of imagery gathered from disparate sources, mostly presents figures in ethereal landscapes. These figures tend to be bearded, hatted, long-haired or seen from behind; figures in disguise, representing opacity, distanced from reality. The landscapes are, for the most part, lush environments, wet and tropical - I wonder if any painter has used green more effectively - and connecting the figures to the seemingly mutable landscapes are shifting elements: water, air, light.

The surface of these paintings is important, with texture used in a purposeful manner while internal boundaries are exaggerated by a violent offsetting of hues. Compositional features, often broadly geometric forms - boats, windows, branches - further divide the focus. The ball in 'Cricket Painting (Paragrand)', set near the centre, between bowler and batsman, seems, for instance, to mark a spatial boundary between one reality and another.

'Black Curtain (Towards Monkey Island)' is a clever, technically accomplished painting that shrouds a nocturnal landscape in a thin window blind, taking the motif of veiled reality quite literally. If this all sounds sinister, it should not. Doig's paintings may inhabit a strange, hallucinatory netherworld but it is a place of enchantment, not menace.

Ken Currie's paintings at the Portrait Gallery tread some similar ground but seem to carry a heavier burden. Like Doig, Currie is drawn to dualistic realities, where things are more than they first appear. Currie is not technically a portrait painter, although to many he may be best known for the 'Three Oncologists' group portrait that haunts the permanent collection here. For that portrait he didn't paint the subjects from life, preferring instead to use plaster-cast 'life masks'. Photographs can deaden and constrict, not a problem for an artist such as Doig, whose interest lies more in the silhouette of a figure than in its actuality, but a serious issue for an artist seeking the nuances of an individual.

The mask has long been a theme in Currie's work and he takes it further in this compelling new exhibition. 'Mould', an exquisite study of a life-mask mould seen from behind, an inverted portrait therefore, baffles at first before revealing its reality. It is a very fine painting, rich inchiaroscuro, and it complements and informs the other work here in both technique and vision. Elsewhere are disquieting scenes, where naked figures, based on the artist himself, lie on biers as if in state, while men - more versions of Currie - prepare plaster masks. The head of the prone figures in 'Nightwork' and 'Plaster Setting' are smothered in dripping white, the plaster pouring off into buckets like the blood of the guillotined. This is powerful painting; the ghosts of Velázquez and Goya are knocking at the door.

Gabriel Orozco is a renowned Mexican artist whose work tries hard to distance itself from the figurative or narrative. His exhibition at the Fruitmarket (until 18 October) centres on one painting, 'The Eye of Go', and presents an abundance of related work. The central piece is a stark black-and-white composition of connected circles. The forms within appear to shift as the eye wanders across the canvas, moving back and forth, in and out of focal planes. It's sculpture on canvas.

The supporting work demonstrates the artist's ongoing interest in the circle motif. Despite the diagrammatic approach to painting, these visual musings reveal a rather painterly thought process of inky sketches and built-up drawings, often based around natural forms. A thumb- or handprint might form the basis of a drawing, so might a leaf or a tampered-with found object. Photographs such as 'Frozen Portable Puddle' nod to the conceptual and recall the works of Dieter Roth. The unusual approach to the curating of this show succeeds, and it offers an effective cross-section of Orozco's varied and at times playful approach to art.

Flying the flag, quite literally, for the true conceptualists at the art festival is Peter Liversidge. Look to the city rooftops and you may be rewarded with a fluttering 'Hello'. InFlags for Edinburghhe invited anyone with a flagpole to fly a white flag with 'Hello' written in black. It is a neat idea, reclaiming the flag from national or political possession. His other Edinburgh contribution,Doppelgängerat the Ingleby Gallery (until 21 September), recreates 'Ein Handschuh', a series of etchings by the 19th-century German Symbolist Max Klinger, which charts the story of a lady's lost glove in a sequence of increasingly bizarre images.

Liversidge converted these etchings to large-scale screenprints, thus exaggerating the detail. Lying on the floor in front of the pictures, as if they have fallen from within, are sculpted, life-size gloves, carved from white Cararra marble. The story of the lost glove, surreal enough in itself, becomes a multilayered exercise in creativity - art embellishing art and recreating itself in the process. As with Doig and Currie, realities are twisted here and the effect is again hallucinatory. Light and dark, life and death, old and new: it all befits Edinburgh rather well."

Claudia Massie

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