question about PNG image format the lossless data compression

If i take simple bitmap ( image without any compression ) and i compress it to PNG format and extract back to the original bitmap - do i get exactly the same image ?

Because the first step of the PNG compression is to do pre-开发者_JAVA技巧compression => filtering ( prediction the current pixel according the the pixel before ) on the original bitmap - and that mean that after it the image will not be same if we will extract it after the compression.

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PNG uses lossless compression, so that the answer is yes, you will get the very same data after decompressing. The filtering stuff does not lose any information, it’s only a preprocessing stage to yield better compression ratios for some common sample patterns (like constant color lines or gradients).