Move guidanceScale as generation parameter (apple#46)

* Move guidanceScale as generation parameter

* Added guidanceScale in CLI

* Reverted identation change

Author: Wanaldino

swift/StableDiffusion/pipeline/StableDiffusionPipeline.swift

@@ -33,9 +33,6 @@ public struct StableDiffusionPipeline: ResourceManaging {
     /// Optional model for checking safety of generated image
     var safetyChecker: SafetyChecker? = nil
 
-    /// Controls the influence of the text prompt on sampling process (0=random images)
-    var guidanceScale: Float = 7.5
-
     /// Reports whether this pipeline can perform safety checks
     public var canSafetyCheck: Bool {
         safetyChecker != nil
@@ -56,20 +53,17 @@ public struct StableDiffusionPipeline: ResourceManaging {
     ///   - unet: Model for noise prediction on latent samples
     ///   - decoder: Model for decoding latent sample to image
     ///   - safetyChecker: Optional model for checking safety of generated images
-    ///   - guidanceScale: Influence of the text prompt on generation process
     ///   - reduceMemory: Option to enable reduced memory mode
     /// - Returns: Pipeline ready for image generation
     public init(textEncoder: TextEncoder,
                 unet: Unet,
                 decoder: Decoder,
                 safetyChecker: SafetyChecker? = nil,
-                guidanceScale: Float = 7.5,
                 reduceMemory: Bool = false) {
         self.textEncoder = textEncoder
         self.unet = unet
         self.decoder = decoder
         self.safetyChecker = safetyChecker
-        self.guidanceScale = guidanceScale
         self.reduceMemory = reduceMemory
     }
 
@@ -112,6 +106,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
     ///   - stepCount: Number of inference steps to perform
     ///   - imageCount: Number of samples/images to generate for the input prompt
     ///   - seed: Random seed which
+    ///   - guidanceScale: Controls the influence of the text prompt on sampling process (0=random images)
     ///   - disableSafety: Safety checks are only performed if `self.canSafetyCheck && !disableSafety`
     ///   - progressHandler: Callback to perform after each step, stops on receiving false response
     /// - Returns: An array of `imageCount` optional images.
@@ -122,6 +117,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
         imageCount: Int = 1,
         stepCount: Int = 50,
         seed: UInt32 = 0,
+        guidanceScale: Float = 7.5,
         disableSafety: Bool = false,
         scheduler: StableDiffusionScheduler = .pndmScheduler,
         progressHandler: (Progress) -> Bool = { _ in true }
@@ -173,7 +169,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
                 hiddenStates: hiddenStates
             )
 
-            noise = performGuidance(noise)
+            noise = performGuidance(noise, guidanceScale)
 
             // Have the scheduler compute the previous (t-1) latent
             // sample given the predicted noise and current sample
@@ -236,11 +232,11 @@ public struct StableDiffusionPipeline: ResourceManaging {
         return states
     }
 
-    func performGuidance(_ noise: [MLShapedArray<Float32>]) -> [MLShapedArray<Float32>] {
-        noise.map { performGuidance($0) }
+    func performGuidance(_ noise: [MLShapedArray<Float32>], _ guidanceScale: Float) -> [MLShapedArray<Float32>] {
+        noise.map { performGuidance($0, guidanceScale) }
     }
 
-    func performGuidance(_ noise: MLShapedArray<Float32>) -> MLShapedArray<Float32> {
+    func performGuidance(_ noise: MLShapedArray<Float32>, _ guidanceScale: Float) -> MLShapedArray<Float32> {
 
         let blankNoiseScalars = noise[0].scalars
         let textNoiseScalars = noise[1].scalars

swift/StableDiffusionCLI/main.swift

@@ -53,6 +53,9 @@ struct StableDiffusionSample: ParsableCommand {
     @Option(help: "Random seed")
     var seed: UInt32 = 93
 
+    @Option(help: "Controls the influence of the text prompt on sampling process (0=random images)")
+    var guidanceScale: Float = 7.5
+
     @Option(help: "Compute units to load model with {all,cpuOnly,cpuAndGPU,cpuAndNeuralEngine}")
     var computeUnits: ComputeUnits = .all
 
@@ -92,6 +95,7 @@ struct StableDiffusionSample: ParsableCommand {
             imageCount: imageCount,
             stepCount: stepCount,
             seed: seed,
+            guidanceScale: guidanceScale,
             scheduler: scheduler.stableDiffusionScheduler
         ) { progress in
             sampleTimer.stop()