/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Still Image Texture Provider for MetalImageFilters.

                Uses the MetalKit texture loader to load an still image into a Metal texture.

 */

import MetalKit

/// Uses the MetalKit texture loader to load a still image into a Metal texture.

class StillImageTextureProvider: NSObject {

    /// The source texture for image filter operations.

    var texture: MTLTexture?

    /// Returns an initialized StillImageTextureProvider object with a source texture, or nil in case of failure.

    required init?(device: MTLDevice, imageName: String) {

        super.init()

        let loader = MTKTextureLoader(device: device)

        let image = UIImage(named: imageName)?.cgImage

        // The still image is loaded directly into GPU-accessible memory that is only ever read from.

        let options = [

            MTKTextureLoaderOptionTextureStorageMode:   MTLStorageMode.private.rawValue,

            MTKTextureLoaderOptionTextureUsage:         MTLTextureUsage.shaderRead.rawValue,

            MTKTextureLoaderOptionSRGB:                 0

        ]

        do {

            let fileTexture = try loader.newTexture(with: image!, options: options as [String : NSObject]?)

            texture = fileTexture

        } catch let error as NSError {

            print("Error loading still image texture: \(error)")

            return nil

        }

    }

}