Methods and systems for transmitting an image with thumbnail data
摘要
說(shuō)明書(shū)
In this example, the first scan is the initial scan for the DC coefficients of the Y, Cr, and Cb channels, minus the lowest two bits. This information is suitable for use as a thumbnail for the image.
The next five scans produce a low quality image. Of these, the first two (scans #2 and 3) capture the second-to-last and last bits, respectively, of the DC coefficients for the Y, Cr, and Cb channels. The third (scan #4) captures the AC coefficients for the Cr chroma channel, while the fourth (scan #5) captures the AC coefficients for the Cb chroma channel. The fifth (scan #6) captures all but the last two bits of the AC coefficients for the Y luma channel.
Typically, the AC coefficients for the luma channel include the most data, and are downloaded last. Thus, the next scan (scan #7), which can be combined with the previous scans to produce a mid-quality image, reads in the second-to-last bit of the AC coefficients for the Y luma channel. The final scan (scan #8) produces the full high-quality image (when combined wi the previous scans) by reading in the lowest bit of the AC coefficients for the Y luma channel.
