Why does converting 64 pixels to 64 DCT functions help to compress a JPEG image?
What will be an ideal response?
Lossy compression is all about removing information that is not vital to the image or sound. If you have an 8 × 8
array of pixels (i.e., the normal image) it is impossible to easily remove information to compress the image. If an
image is transformed into DCT coefficients, the data becomes ordered in the sense that the 64 DCT coefficients
are arranged from 1 to 63 with 0 being the D.C. coefficient (the average luminance) and the other coefficients
corresponding to horizontal and vertical waves of increasing frequency. The highest numbered coefficients are
the highest visual frequencies and these often tend to be low values (if you photograph a sky with little detail,
there are no high?frequency visual components). Consequently, you can sometimes reduce these coefficients to
zero with little effect on the image.
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Answer the following statement true (T) or false (F)
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Fill in the blank(s) with the appropriate word(s).