In JPEG, there is a type of progressive image that you may have seen on the network, that is, the one that first appears a blurred image and then gradually becomes clearer. Compared with baseline JPEG, this image has some advantages in network transmission, allowing users to see the image first and provide a better user experience UX.
Generally, baseline JPEG is stored in the top-to-bottom scan mode, while the progressive method is to divide the file into multiple scans. During the first scan, use a very low quality setting, so that the occupied space is very small. Next, the scan will gradually increase the quality, and each scan will be added to the existing data, so that the file size is basically the same as that of baseline. In general, JPEG ssive JPEG organizes the same data into a slightly more complex order.
However, when progressive JPEG is used for decompress, it will occupy a large amount of memory. In the embedded system, it will cause out-of-memory.
Especially when it exceeds 720*480, the occupied memory sometimes reaches 16 Mb.