Most of them are automatically increased or even reduced by the resolution when uploading to reduce the storage capacity, which is called "slimming"! Generally speaking, the resolution can be maintained by selecting the original image, but the user may not be able to adjust the compression ratio. At present, the commonly used JPEG format is lossy compression. The greater the compression ratio, the easier it is to blur the details, but the details of each photo are different and the compression results are different. If you have a choice, don't choose to lose weight.