PSNR, SSIM, and MSE are all commonly used metrics for assessing image quality. PSNR measures the ratio between the maximum possible value of a signal and the power of the corrupting noise, while SSIM measures the similarity between two images based on their luminance, contrast, and structure. MSE measures the average of the squares of the errors between two images.

Image quality assessment is used to determine the subjective quality of an image (how pleasing it is to the human eye), the objective quality of an image (how well it matches a reference image), and to compare the quality of two or more images.

MOS, SUS, and NPS are all subjective image quality assessment methods. MOS is a measure of the average opinion of a group of people about the quality of an image, SUS is a measure of the usability of a system, and NPS is a measure of the likelihood that a customer would recommend a product or service to others.

PSNR, SSIM, and MSE are all objective image quality assessment methods. PSNR measures the ratio between the maximum possible value of a signal and the power of the corrupting noise, while SSIM measures the similarity between two images based on their luminance, contrast, and structure. MSE measures the average of the squares of the errors between two images.

Subjective image quality assessment is based on the opinions of human observers, while objective image quality assessment is based on mathematical calculations. Subjective image quality assessment is more expensive than objective image quality assessment, but it is also more accurate.

Noise, blur, and JPEG compression artifacts are all common types of image distortion. Noise is unwanted variation in the intensity of an image, blur is the loss of detail in an image due to motion or camera shake, and JPEG compression artifacts are the result of compressing an image using the JPEG algorithm.

Median filter, Gaussian filter, and bilateral filter are all common methods for reducing noise in images. Median filter replaces each pixel with the median value of its neighbors, Gaussian filter blurs an image by convolving it with a Gaussian kernel, and bilateral filter blurs an image while preserving edges.

Unsharp mask, Wiener filter, and Richardson-Lucy deconvolution are all common methods for reducing blur in images. Unsharp mask sharpens an image by subtracting a blurred version of the image from the original image, Wiener filter removes noise from an image while preserving edges, and Richardson-Lucy deconvolution is a more sophisticated method for deblurring images.

Deblocking filter, ringing filter, and artifact removal filter are all common methods for reducing JPEG compression artifacts in images. Deblocking filter removes the blocking artifacts that are often visible in JPEG images, ringing filter removes the ringing artifacts that are often visible around sharp edges in JPEG images, and artifact removal filter removes other types of artifacts that can be caused by JPEG compression.

Higher image quality usually results in larger file sizes because more information is needed to represent a higher quality image. However, the relationship between image quality and file size can vary depending on the image format. For example, JPEG images can be compressed to reduce their file size without significantly affecting their quality, while PNG images cannot be compressed as much without losing quality.

LIVE Image Quality Assessment Database, TID2013 Image Quality Assessment Database, and Waterloo Exploration Image Quality Assessment Database are all common image quality assessment datasets. These datasets contain a variety of images with different levels of quality, and they are used to train and evaluate image quality assessment algorithms.

The main challenges in image quality assessment are the subjective nature of image quality, the variety of image content, and the computational complexity of image quality assessment algorithms. Image quality is subjective because different people may have different opinions about the quality of an image. The variety of image content makes it difficult to develop image quality assessment algorithms that work well for all types of images. The computational complexity of image quality assessment algorithms can make them slow and expensive to use.

Some of the latest trends in image quality assessment include the use of deep learning for image quality assessment, the development of no-reference image quality assessment algorithms, and the use of image quality assessment for image enhancement. Deep learning algorithms have been shown to achieve state-of-the-art performance on image quality assessment tasks. No-reference image quality assessment algorithms do not require a reference image to assess the quality of an image. Image quality assessment can be used to improve the quality of images by identifying and correcting distortions.

Image quality assessment has a wide range of applications, including image compression, image enhancement, and image restoration. Image quality assessment can be used to select the best compression algorithm for a given image, to improve the quality of an image by removing noise or blur, and to restore a damaged image to its original quality.

The future of image quality assessment is bright. Researchers are developing more accurate and efficient image quality assessment algorithms, and new applications for image quality assessment are being discovered. Image quality assessment is also being integrated into image processing pipelines, which is making it easier for developers to create high-quality images.