Lossless image compression

Lossless image compression. Loading the image, doing something to it, and then saving it again will ultimately result in image degradation. Simply put, it means converting a large file into a smaller file. Run train. Jan 1, 2023 · Lossless image compression is useful for a variety of image formats, including BMP, RAW, PNG, and GIF. ; Masmoudi, A. Nov 24, 2021 · Instead I stumbled into a solution for the former: a lossless image format that competes with PNG for some use cases. In contrast to recent autoregressive discrete probabilistic Nov 23, 2021 · Despite extensive progress on image generation, common deep generative model architectures are not easily applied to lossless compression. I load the image with PIL: img = Image. Find out how lossless compression is used for text, images, audio, and other data types. There are several image compression algorithms: Oct 4, 2023 · Lossy vs. Through comparison, we can reach a Use this image compression service to reduce the size of an image. Lossy methods are especially suitable for natural images such as Mar 25, 2024 · Lossless Image Compression. There are two types of compression: lossless, which reduces the file size without reducing quality, and lossy, which reduces the size and quality. [13] In these schemes, some loss of information is accepted as dropping nonessential detail can save storage space. Both compression methods have advantages and disadvantages and are practically applied in many fields. , x, the essential problem in lossless data compression is to process the Jun 8, 2021 · For lossless image compression, a lot of research work has been carried out . Easily reduce image size by up to 80% with lossy compressions using this free tool. 2015, 9, 1021–1027. In this paper, we propose PILC, an end-to-end image lossless compression framework Oodle Lossless Image is a new image compression algorithm that achieves very high compression ratios, but with incredibly fast decompression. Lossy Compression Techniques Lossy compression, as the name implies, is a technique that does not return the exact original image after decompression. Our integrated features ensure a smooth workflow, delivering optimized images that are ready for your website. 10 MB Reduction of size: 9. ch vangool@vision. The numerical results indicate that our method achieves the highest compression ratio with an average improvement of 38% over JPEG2000, thus confirming the Mar 25, 2024 · Residual coding has gained prevalence in lossless compression, where a lossy layer is initially employed and the reconstruction errors (i. py to train the DLPR coding system with $\lambda=0. The TDC generates the second best compression and Mar 18, 2024 · Lossless compression is the ideal choice, because all the data is fully preserved and yet the image takes up much less space. In this paper, we propose a unified and Lossless compression is generally used for so-called "discrete" data, such as database records, spreadsheets, word-processing files, and even some kinds of image and video information. Or get 2x more storage potential if you are using the FFV1 video-compression thing. View Results: TEST IMAGES. Jul 16, 2024 · Conclusion. To better understand the difference in file size, for lossy compression a size reduction of 85% can be achieved for an image, while, using a lossless compression, for the same image only a 5% reduction is recorded. (Don Gourley et al. But still, researchers are trying hard & report some of the medical image compression techniques producing images with minimum loss. 2 days ago · WebP is a modern image format that provides superior lossless and lossy compression for images on the web. Herein, we propose a residual coding framework for 3D medical images, involving the off-the The lossless image compression technique has a great application value in distortion-sensitive applications. lossless compression. LOCO-I (LOw COmplexity LOssless COmpression for Images) is the algorithm at the core of the new ISO/ITU standard for lossless and near-lossless compression of continuous-tone images, JPEG-LS. With the fast development of deep learning techniques, deep neural networks have been used in this field to achieve a higher compression Feb 26, 2019 · The necessity of data transfer at a high speed, in fast-growing information technology, depends on compression algorithms. FLAC is a lossless audio format, while MP3 is a lossy audio format. “Lossless compression” is the art of reducing file sizes without sacrificing image quality. By combining simplicity with the compression potential of Jun 9, 2016 · A recent lossless image compression scheme by Kim et al. Yao Wang, NYU-Poly EL5123: Lossless Compression 4 Image Coding Standards by ITU and ISO • G3,G4: facsimile standard • JBIG: The next generation facsimile standard – ISO Joint Bi-level Image experts Group • JPEG: For coding still images or video frames. Mar 3, 1995 · The critical task in lossless data compression is finding good models for the data under consideration, and algorithms that 'learn' the parameters of the model that best describes the data and achieve rates that are asymptotically optimal are known as oplimal universal coding schemes. In contrast to recent autoregressive discrete probabilistic Aug 30, 2022 · Lossless image compression is an essential research field in image compression. Oct 11, 2019 · A new arithmetic coding model for a block-based lossless image compression based on exploiting inter-block correlation. Inspired by 24-bit RGB lossless images compression benchmark (LPCB) authored by Alex Rhatushnyak. However, the throughput for most of them is less than 1 MB/s even with the most advanced AI accelerated chips, preventing them from most real-world applications, which often require 100 MB/s. In recent years, learning-based lossless image compression methods, combining neural network predictions with residuals, have achieved performance comparable to traditional non-learning algorithms. Learn what lossless compression is, how it works, and what are its advantages and disadvantages. Therefore, in this paper, we explore the Aug 19, 2024 · Image compression is reducing an image’s file size while maintaining an acceptable level of visual quality. com/c/Kinsta?sub_confirmation=1Digital images are an Jul 8, 2022 · Figure 21 shows a set of 6 24-bit RGB images. In this paper we survey existing coding Sep 19, 2019 · The goal is to design an effective lossless compression scheme that is scalable to high-dimensional data, like images. JPEG-LS, as a mature lossless compression standard, is widely adopted for its excellent compression ratio. May 9, 2023 · There are two forms of image compression: lossless and lossy. Modified 7 years, 3 months ago. But even with these advances, mathematically lossless image compression (MLLIC) ratios for natural images still fall short of the bandwidth and cost-effectiveness requirements of most practical imaging and Jan 3, 2023 · The compression of images is carried out by an encoder and output a compressed form of an image. Lina J. Image Compression. It is beneficial to compress those existing JPEG files without introducing additional distortion. Surprisingly, we observe (§III) that even standard lossless Jan 8, 2024 · First, we use lossy compression to accept a reduced image quality while achieving a much smaller file size. Lossy Compression Techniques Lossy compression, as the name implies, is a technique that does not return the exact original image after decompres-sion. The proposed coding approach employs a deep-learning-based method to compute the prediction for each pixel, and a context-tree-based bit-plane codec to encode the prediction errors. in focuses on encoding CFA images. Website builders should carefully consider the needs of their end users and test the speed of their websites when deciding between lossy and lossless image compression. Table 5 and Figure 22 illustrate that TIFF has the best lossless compression on this set of images. Image compression is the application of data compression on digital images, where the objective is to reduce the redundancy of the image data. If you're behind a web filter, please make sure that the domains *. Lossy and Lossless Image Compression¶ When we compress a file, we do this because we want to temporarily make it smaller (like for sending over email), or we want to permanently make it smaller (like for showing images on the internet). We further argue that the binarized version of an image captures its fundamental spatial structure. To run benchmark, see RunBench. Lossless optimized images are pixel-by-pixel identical with the originals, but they offer a smaller size reduction compared to either Lossy or Glossy processed files. Lossless compression is preferred for archival purposes and often for medical imaging, technical drawings, clip art, or comics. The goal of lossless image compression is to represent an image signal with the smallest possible number of bits without loss of any information, thereby speeding up transmission and minimizing storage requirements. View Results LOSSY COMPRESSION. The BBWCA scheme was employed for lossless compression of CFA images. Optimize and compress JPEG, PNG, SVG, GIF and WEBP images online. Lossy compression permanently removes certain data to significantly decrease file size, making it perfect for multimedia but inappropriate for crucial data. Compression reduces file size without quality loss, allowing faster transfers and saving storage space. Technical Details. Learn about the principles and methods of lossless compression, which allows the original data to be perfectly reconstructed from the compressed data. It is shown that Nov 30, 2018 · We propose the first practical learned lossless image compression system, L3C, and show that it outperforms the popular engineered codecs, PNG, WebP and JPEG 2000. With the fast development of deep learning techniques, deep neural networks have been used in this field to achieve a higher compression rate. If you're seeing this message, it means we're having trouble loading external resources on our website. A carefully chosen set of high-resolution high-precision natural images suited for compression algorithm We propose the first practical learned lossless image compression system, L3C, and show that it outperforms the popular engineered codecs, PNG, WebP and JPEG 2000. py to encode and decode test images of arbitrary sizes. Aug 25, 2023 · Lossless image compression. Methods based on pixel-wise autoregressive statistical models have shown good performance. To overcome Lossless Coding. The ‘multiresolution seamless image database’ widely known as MrSID, a propriety format that is commonly used for geographic information Image compression may be lossy or lossless. There are mainly two types of image compression method - Lossy Compression and Lossless Jul 6, 2021 · A new lossless compression scheme is presented and named as Huffman Based LZW Lossless Image Compression using Retinex Algorithm which consists of three stages: in the first stage, a Huffman coding is used to compress the image, and in the second stage all Huffman code words are concatenated together and then compressed with LZW coding and decoding. Applications of lossless and lossy compression. Lossy compression: Discards some data to achieve smaller file sizes, potentially reducing image quality Where does Python compress/change the picture and how (if possible) can I subdue it? I could think of some passages, which might be the one compressing. What is lossy and lossless compression? Lossless compression An algorithm that allows an image to be reduced in size without losing quality. For example, PNG and GIF formats are used during lossless compression. ch timofter@vision. If $\tau=0$, the special Mar 15, 2002 · Lossless (reversible) image compression techniques preserve the information so that exact reconstruction of the image is possible from the compressed data. 1 day ago · Lossless image compression techniques shrink the image size to improve the transmission efficiency and reduce the occupied storage space while ensuring the quality of the image is lossless. Such data compressing technique prefers for higher quality upon size reduction and allows you to view photos in a much more detailed manner. g. However, the sequential processing Lossless Compression. a run of the previous pixel Dec 21, 2022 · Lossless compression preserves details better than lossy compression How Lossless Compression Works. LOSSLESS COMPRESSION. In the processes of compression, the mathematical transforms play a vital role. Lossless compression does what it says on the label: It compresses an image’s file size as much as possible without affecting the visible quality. Karam, in Handbook of Image and Video Processing (Second Edition), 2005 1 Introduction. Audio files that use lossless compression are roughly half of the size of the uncompressed original at the same sample rate. Quality: JPEG XL lossless mode is as good as it gets as of 2024. When choosing a tool for image compression, remember to take into consideration whether the image compressor will result in any quality loss for your images. In the early 1990s, lossy compression methods began to be widely used. Some of these strategies happen within your WordPress dashboard, whereas others rely on external software. There are two main types of compression: Lossless compression: Preserves all original data, allowing exact image reconstruction. Jun 11, 2021 · The results of Table 2 indicate that the average compression ratio with soft compression is obviously higher than other image lossless compression methods. Because of the nature of JPEG files, only lossy compression is possible with these kinds of images. JPEG and WebP are lossy image formats. You can use a few different methods to apply lossless compression to your images. Multimed. Aug 25, 2023 · JPEG is one of the most popular image compression methods. Compress image files while preserving quality. For instance, we have JPEG and WebP formats for lossy compression. However, JPEG-LS has a contextual Read-After-Write (RAW) issue Jun 5, 2024 · Thus, we divide the overall design of a lossless image compression scheme into three parts that exploit corresponding redundancies. [Google Scholar] Masmoudi, A. In this first part of our work, we propose a scheme for lossless compression of binary images. Jun 5, 2024 · Lossless image compression is required in various applications to reduce storage or transmission costs of images, while requiring the reconstructed images to have zero information loss compared to the original. Viewed 9k times 4 I am looking for a way to encoding When you compress a digital file, you remove bits of information in order to reduce its overall size. At the core of our method is a fully parallelizable hierarchical probabilistic model for adaptive entropy coding which is optimized end-to-end for the compression task. [5] This mode is quite popular in the medical imaging field, and defined as an option in DNG standard, but otherwise it is not very widely used because of complexity of doing arithmetics on 10, 12, or 14bpp values on typical embedded 32-bit processor and a little resulting gain in Jul 26, 2018 · Other applications of lossless compression include the compression of image for camera system [191], the storage and transmission of thermal images captured by Nano-satellite [195] and remote sensing applications such as monitoring forest fires and determining the soil moisture [196]. Lossless compression ensures that all image information is preserved, while lossy compression loses information in the process. Your images become lighter without losing their charm. Examples include TIFF, GIF, and PNG. , financial data) could pose a problem. Lossless compression is an alternative for the quality-conscious site owner. May 8, 2024 · In conclusion, lossless image compression is a crucial area of research that addresses the need for efficient data representation while preserving the integrity of digital images. As the name implies Mar 20, 2023 · 2 Ways to Apply Lossless Compression to Your Images. Photo websites, on the other hand, should use lossless compression. Compression that is also accompanied by a decom-pression process, returning a model to its original size and usability. One of the most common lossless formats is PNG , a widely used format that reduces file size by identifying patterns and compressing those patterns together. 03$. . Lossless compression reduces bits by identifying and eliminating statistical redundancy. Online, free, and easy to use – compress an image using Img2Go. This overhead can only be partially eliminated with elaborate schemes such as bits-back coding, often resulting in poor single-sample compression rates. Results for lossy compressors including Jpeg, Jpeg2000 and HD-Photo/Jpeg-XR. See test results and examples of PNG, WebP, AVIF, and JPEG XL compression. Lossless compression techniques are for when we want to temporarily reduce information. It touches every pixel just once. QOI encodes and decodes images in a single pass. WebP lossless images are 26% smaller in size compared to PNGs. The trade-off is that you won’t see a significant reduction in image file size. Ask Question Asked 13 years, 8 months ago. Jul 18, 2024 · Compression Options: LZW and ZIP: Both are lossless compression methods, preserving image quality. Nov 6, 2021 · photos photography jpeg encoder images decoder lossy codec image-compression lossless-compression-algorithm lossless-images lossy-compression jxl lossy-image-compression lossless-image-compression jpeg-xl What is Image Compression? Image Compression is the method to reduce the size of the image file by deleting some of its unnecessary internal data without any loss of information. Use an Image Compression Plugin Lossless and near-lossless image compression is of paramount importance to professional users in many technical fields, such as medicine, remote sensing, precision engineering and scientific research. Typically, compressions using lossless operation mode can achieve around 2:1 compression ratio for color images. The lossless compression algorithms used are PNG, TIFF, and TDC. , 2009) Lossless compression will usually produce a file that is half the original file in size, while lossy compression can reduce image size more than lossless compression can. In our image formats that support lossless image compression. The presented research establishes a promising direction for lossless image compression, combining CLAHE, two-channel encoding, and adaptive arithmetic coding. Let’s take a look at two different compression options! 1. In DLPR_nll folder, we provide the DLPR coding system for scalable near-lossless compression. In this paper, a new lossless image compression algorithm is proposed, which uses both wavelet and fractional transforms for image compression definition of compression typically used for networking and storage. Lossless compression comes in handy when the original image data is essential for referential or editing purposes. Maintaining quality of data reconstructed at high compression rate is a very difficult part of the data compression technique. We propose the first practical learned lossless image compression system, L3C, and show that it outperforms the popular engineered codecs, PNG, WebP and JPEG 2000. This is a matter of concurrently solving two problems: choosing a statistical model that closely captures the underlying distribution of the input data and May 21, 2024 · There are two categories of compression techniques, lossy and lossless. ethz. If you need to alter and save an image without losing any of the data you need to use a lossless format such as TIFF, PNG or BMP. Compress, resize and rename your photos for free. In our pursuit of developing a lossless image compression scheme that performs better than all other schemes over all types of images, is amenable for rigorous performance analysis, and can provided guaranteed compression for a given type of images, we step back and ask the most basic question related to image compression: where does the information lie in an image? With Tinify's online optimizer, image conversion and compression are seamlessly combined into one powerful tool. A typical lossless image compression system contains a probability model and an entropy codec. May 7, 2024 · Image compression methods are divided into two categories: lossy compression and lossless compression . ch michaelt@nari. The state-of-the-art lossless image compression algorithms are Run-Length Encoding (RLE) , the entropy coding , and the dictionary-based coding . Practical Full Resolution Learned Lossless Image Compression Fabian Mentzer Eirikur Agustsson Michael Tschannen Radu Timofte Luc Van Gool mentzerf@vision. Jul 27, 2021 · Learn how lossless compression works and which image formats are best for graphics, logos, and text. The TIFF format is added as it is widely used for creating medical imaging datasets. When applied to the whole world of media (not only images), it means that the initial data could be perfectly restored from the compressed version. In contrast, lossless image compression techniques retain the original quality but do not compress the image as efficiently. Audio: WAV is a container file often used to contain lossless audio, although it is also capable of containing lossy audio. Apr 1, 2022 · To demonstrate the validity of this compression scheme, its compression performance was compared with current state-of-the-art lossless image compression methods on 10 blind CTC datasets. 26% Oct 28, 2021 · Image compression techniques can be broadly divided into two categories, namely (I) lossy image compression and (II) lossless image compression. But despite rapidly growing research interests in learning-based image compression, no published method offers both lossless and near-lossless modes. Types of image compression. Pixels are encoded as. You can save all your TIFF compressed, lossless formatted images there. This definition encompasses among other things all forms of lossless compression. Lossless image compression is an essential research field in image compression. Given a finite sequence x1, x2, . youtube. Simply drag and drop your images onto the web interface, and watch as they are effortlessly converted to WebP, PNG, or JPEG. e. . ee. Considerations: Compressed TIFF files can be slightly slower to work with due to processing. While lossless compression can reduce image file sizes by as much as 40%, it is still less effective than lossy compression for reducing file size and optimizing images for the web. Oct 29, 2014 · UPDATE: As a commenter mentioned, 100% quality still does not mean lossless compression when using JPEG. Recently, learning-based image compression methods achieved impressive performance compared with traditional lossless methods, such as WebP, JPEG2000, and FLIF. This benchmark uses 62 uncompressed images (total 751 MB). open(element) I create a new picture, which is black: newImg = Image. Aug 24, 2021 · Lossless image compression is an important technique for image storage and transmission when information loss is not allowed. Results for lossless compressors, including Jpeg-ls, Jpeg2000, HD-Photo/Jpeg-XR. It is conceived as a "low complexity projection" of the universal context modeling paradigm, matching its modeling unit to a simple coding unit. Feb 1, 2022 · Lossless image compression techniques. Here, we ran the same image through the Shortpixel lossless compressor: Lossless compression test using the Shortpixel Image Compressor: Original Image Size: 1. Find out which file types use lossless compression and how to apply it to your photos. That’s because lossless compression only removes additional, non-essential data automatically added by the device used to take the photo. Please adjust input_path and tau to evaluate your own images. ch aeirikur@vision. If you want your images to remain untouched, then select this option. There are two types of compression: lossless and lossy. A slightly worse compression ratio, but magnitudes less complexity. The latter method is the most common in image compression Jan 15, 2022 · However, lossy isn’t the only option. org and *. In this paper, we propose a deep learning based method to further compress JPEG images losslessly. Many hardware JPEG-LS compressors are proposed on FPGAs and ASICs to achieve high energy efficiency and low cost. Image compression can be lossy or lossless. Using WebP, webmasters and web developers can create smaller, richer images that make the web faster. Second, we use lossless compression to preserve data and information during compression. It compresses to tiny sizes like the highest compression lossless image formats (WebP, FLIF, JPEG2000, PNG, etc), but it destroys them in decode speed -- usually 5-10x faster than PNG and 200-500x faster Lossy vs lossless compression- which one is right for your images? 🤔 👉 Subscribe: https://www. In RLE, data is stored as a single value and the count of the same consecutive values, so the code length is decreased Lossless Coding. This type of compression refers to a set of image compression algorithms that do not affect image quality, while still providing more optimal results in terms of file size. However, do you really need byte-to-byte lossless compression? Lossy image compression algorithms can benefit greatly from removing unnecessary details that would not be seen by human eye anyways. Signal Image Video Process. However, there are still many impressive lossy compression methods that can be applied to lossless compression. ch Lossless image compression is a crucial aspect of image processing and storage, vital for maintaining image quality while reducing file size without any loss of information. It utilises a hierarchical predictor and a context-adaptive arithmetic encoder and is referred as Hierarchical Prediction and Context Modelling (HPCM) algorithm. This project proposes a lossless method of image compression and decompression using the Huffman coding technique. Run test. Jan 24, 2024 · Recently, DNN models for lossless image coding have surpassed their traditional counterparts in compression performance, reducing the bit rate by about ten percent for natural color images. Whilst each uses different techniques to compress files, both have the same aim: To look for duplicate data in the graphic (GIF for LZW) and use a much more compact data representation. Lossy compression methods, especially when used at low bit rates, introduce compression artifacts. Jan 16, 2024 · For example, lossless compression may reduce a PNG image to 30-40% of its original size. For example, VAEs suffer from a compression cost overhead due to their latent variables. In terms of digital files, compression is the act of encoding information using fewer bits than what’s found in the original file. proposed a local bit-back coding scheme and realized lossless image compression with Jan 25, 2024 · The file formats like RAW, BMP, GIF, and PNG can all benefit from lossless-image-compression algorithms. new("RGB",(imgWidthNew,imgHightNew),(0,0,0,0)) In , Ma et al. The probability model is built up from a statistical model This repo shows the performance of several state-of-the-art lossless image compression formats/methods when compressing 8-bit grayscale images. org are unblocked. Existing lossless image compression methods either have simple design but poor compression performance, or complex design, better performance, but with no performance guarantees. md Types of Compression Techniques Image compression techniques can be broadly divided into two categories, namely (I) lossy image compression and (II) lossless image compression. proposed a wavelet-like transform for lossy and lossless image compression, which can be considered as a special flow model. 18 MB Post lossless compression image size: 1. Figure 1 shows the results of two methods of image compression. The underlying principle of the residual coding revolves around the exploration of priors based on context modeling. In this article, we will delve into the intricacies of lossless image compression, exploring its definition, functioning, benefits, common techniques, comparison of formats Sep 3, 2021 · Some examples of lossless compression include the FLAC and ALAC audio codecs, ZIP archives, and PNG images. Specifically, we propose a Multi-Level Parallel Conditional Modeling (ML-PCM) architecture, which enables parallel decoding in different This paper proposes a novel approach for lossless image compression. Lossless compression is mainly used to compress: images; sound; text; It is generally the technique of choice for detailed product images, photography showcases, text files and spreadsheet files, where the loss of picture quality, words or data (e. Uncompressed – an uncompressed Raw file contains all the data, but without any sort of compression algorithm applied to it. Unlike lossy compression, which discards certain parts of a file to create a smaller and lower-fidelity version of the original, lossless compression saves file space by rewriting the data more efficiently. ; Puech, W. Lossless compression. Lossless compression is generally used in situations where image quality is more important than disk space or network performance, such as for product images or to showcase artwork. Pros and Cons of Lossless Compression. The research for providing lossless compression using CNN is still in its infancy, as the loss distorts at every step at the time of encoding information. In , Ho et al. Feb 25, 2021 · Lossless image compression is an important technique for image storage and transmission when information loss is not allowed. First, a novel deep learning-based predictor is proposed to estimate the residuals produced by traditional prediction methods. A flow chart of the process of the compression of the image can be represented as: In this article, we try to explain the overview of the concepts involved in the image Jan 24, 2024 · But even with these advances, mathematically lossless image compression (MLLIC) ratios for natural images still fall short of the bandwidth and cost-effectiveness requirements of most practical imaging and vision systems at present and beyond. An improved lossless image compression based arithmetic coding using mixture of non-parametric distributions. – ISO Joint Photographic Experts Group Nov 6, 2015 · Images: RAW, BMP, and PNG are all lossless image formats. Among them, the LOCO-I/JPEG-LS algorithm benefits high lossless compression ratio and low computational complexity and thus is widely used for various real Learn how to choose between lossy and lossless compression methods for your digital photos, based on file size, quality, and purpose. Other image compres-sion techniques, such as JPEG 2000 [3], WebP[4], and HEVC [5] support both lossy and lossless image compression. Additionally, you can use "drive compression", which is 100% lossless and just fits odd images which don't fit into "whole chunks", back into a portion of a whole-chunk, with other partial With Tinify's online optimizer, image conversion and compression are seamlessly combined into one powerful tool. Jun 10, 2022 · Generative model based image lossless compression algorithms have seen a great success in improving compression ratio. Compare the pros and cons of each method, and see examples of common applications and file types. However, there are still many impressive lossy compression methods that can be applied to In the late 1980s, digital images became more common, and standards for lossless image compression emerged. , residues) are then losslessly compressed. Neural networks, owing to their outstanding image estimation capabilities, have provided new avenues for lossless compression. Data compression is a technique for reducing data size that can be divided into two categories: lossy and lossless. Unlike lossy compression, lossless image compression won’t reduce image quality. May 16, 2017 · Javascript lossless image compression. kasandbox. Text compression is a significant area for lossless compression. kastatic. fmjymh sebqnx ucpjim mxlu lond gckei usxfm koo axn juewuc