Israeli technology company ICTV has developed a method to optimize JPEG compression, JPEGmini, which reduces image file size by 50%-80% without causing visible loss to the naked eye. In an interview with the developer of the technology, he mentioned that "sometimes you choose a higher image quality in Photoshop, but in essence it causes a loss of image quality." In an article called JPEG Compression Quality from Quantization Tables, we saw this: “Many people don’t know that there is a 'fake' in Photoshop's method of defining image quality. Level 6 image quality is the last level of applied chroma sampling. At 7th and higher levels, Photoshop does not perform chroma sampling. Since the color information from level 6 to level 7 is doubled, the file size is significantly increased. “However, Adobe seems to be trying to establish a relationship between the image quality level and the file size. Therefore, Adobe has a higher compression of the 7-quality image. This means that the 7-level image is actually 6 The quality of the quality is worse (at least for the brightness details). "The only advantage of the 7-level quality image is that the chrominance details are not sampled. Therefore, the 7-level quality may have some advantages from the color information, but this advantage will be offset by a higher compression ratio." In the field of digital image processing, chroma sampling refers to expressing color (chrominance) information using a lower resolution of luminance information when representing an image. Chroma sampling is typically used when digitally simulating analog component video or YUV signals. Since the human eye's sensitivity to chromaticity is less than sensitivity to brightness, the chrominance component of the image does not need to have the same sharpness as the luminance component, so many video systems perform lower (relative luminance channel) resolution on the color difference channel. Sampling (for example, sampling frequency). This reduces the total bandwidth of the video signal without significantly degrading the picture quality. The chrominance values ​​lost due to sampling are replaced by interpolated values, or previous chrominance values. --Wikipedia Regarding the chroma sampling in Photoshop, the original text explains: “In Photoshop, the software determines whether to perform chroma sampling based on the image quality level selected when saving the image. Photoshop CS2 uses 1×1 sampling for 7-12 quality (no sampling); 2×2 for 0-6 - Chroma sampling in both horizontal and vertical directions. It should be noted that such chroma sampling will lose a lot of information compared to chroma sampling performed by most digital cameras (except for some low-end cameras). . “Photoshop only provides 2×2 or 1×1 (no sampling) chroma sampling. Most digital cameras use 2×1 sampling. Therefore, you must choose or double the horizontal color resolution (7 or above). , or lose the color resolution in the vertical direction (0-6 levels)." So what conclusion can we draw from it? Simply put, don't use level 7 image quality when saving JPEG files. If you need a smaller image size, choose level 6; if you choose better image quality, use level 8 or higher (even if level 12 will still compress the image). Article source address: http:// According to the research of the major medical, it continues to remind people that a sedentary lifestyle is closely related to many health risks, such as heart disease,back or neck pain, high blood pressure, and obesity. Adjustable Computer Desk,Office Standing Adjustable Desk,Hand Crank Standing Desk,Adjustable Height Office Standing Desks CHEX Electric Standing Desk , https://www.sjqxhdesk.com
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