GENERATING HIGH FIDELITY IMAGES WITH SUBSCALE PIXEL NETWORKS AND MULTIDIMENSIONAL UPSCALING
The unconditional generation of high fidelity images is a longstanding benchmarkfor testing the performance of image decoders.Autoregressive image modelshave been able to generate small images unconditionally, but the extension ofthese methods to large images where fidelity can be more readily assessed hasremained an open problem.Among the major challenges are the capacity to encodethe vast previous context and the sheer difficulty of learning a distribution thatpreserves both global semantic coherence and exactness of detail.To address theformer challenge, we propose the Subscale Pixel Network, a conditionaldecoder architecture that generates an image as a sequence of image slices of equalsize.The SPN compactly captures image-wide spatial dependencies and requires afraction of the memory and the computation.To address the latter challenge, wepropose to use multidimensional upscaling to grow an image in both size and depthvia intermediate stages corresponding to distinct SPNs.We evaluate SPNs on theunconditional generation of CelebAHQ of size 256 and of ImageNet from size 32to 128.We achieve state-of-the-art likelihood results in multiple settings, set upnew benchmark results in previously unexplored settings and are able to generatevery high fidelity large scale samples on the basis of both datasets.
We show that autoregressive models can generate high fidelity images. An architecture utilizing decoder, size-upscaling decoder, and depth-upscaling decoder components to tackle the problem of learning long-range dependencies in images in order to obtain high fidelity images.This paper addresses the problem of generation to high fidelity images, successfully showing convincing Imagenet samples with 128x128 resolution for a likelihood density model.