图像质量

峰值信噪比、结构相似性指数 (SSIM)；无参考图像质量指标；基于测试图的质量测量

质量指标提供图像质量的客观分数。全参考算法将输入图像与无失真的原始参考图像进行比较。无参考算法将输入图像的统计特征与从图像数据库导出的一组特征进行比较。

经过标准化的测试图包含视觉特征，例如倾斜边缘、灰色补片和彩色补片。这些特征支持测量对应的图像质量特征，例如锐度和颜色准确度。

函数

`immse`	均方误差
`psnr`	Peak signal-to-noise ratio (PSNR)
`ssim`	用于测量图像质量的结构相似性 (SSIM) 索引
`multissim`	Multiscale structural similarity (MS-SSIM) index for image quality
`multissim3`	Multiscale structural similarity (MS-SSIM) index for volume quality

`brisque`	Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE) no-reference image quality score
`fitbrisque`	Fit custom model for BRISQUE image quality score
`brisqueModel`	Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE) model
`niqe`	自然图像质量评估方法 (NIQE) 无参考图像质量分数
`fitniqe`	Fit custom model for NIQE image quality score
`niqeModel`	Naturalness Image Quality Evaluator (NIQE) model
`piqe`	Perception based Image Quality Evaluator (PIQE) no-reference image quality score

`esfrChart`	Imatest edge spatial frequency response (eSFR) test chart
`colorChecker`	Calibrite ColorChecker test chart
`measureSharpness`	Measure spatial frequency response using Imatest eSFR chart
`measureChromaticAberration`	Measure chromatic aberration at slanted edges using Imatest eSFR chart
`measureColor`	Measure color reproduction using test chart
`measureNoise`	Measure noise using Imatest eSFR chart
`measureIlluminant`	Measure scene illuminant using test chart
`displayChart`	Display test chart with overlaid regions of interest
`displayColorPatch`	Display measured and reference color as color patches
`plotSFR`	Plot spatial frequency response of edge
`plotChromaticity`	Plot color reproduction on chromaticity diagram

Image Quality Metrics
Image quality metrics provide an objective measure of image quality. Each metric has a different computational complexity and agreement with the human perception of image quality.
Train and Use No-Reference Quality Assessment Model
Learn how to fit a custom model and how to use the model to compute a no-reference quality score.
Obtain Local Structural Similarity Index
Measure the quality of regions of an image when compared to a reference image.
Compare Image Quality at Various Compression Levels
Compress an image by various compression levels, then compute and plot the structural similarity quality metrics at each level.

Anatomy of the Imatest Extended eSFR Chart
An Imatest^® eSFR chart has visual features including slanted edges, gray patches, color patches, and registration points, for image quality measurements.
Evaluate Quality Metrics on eSFR Test Chart
Measure sharpness, chromatic aberration, noise, illumination, and color accuracy on an Imatest Extended eSFR chart.