Domagoj Saric wrote:
"Phil Endecott" <spam_from_boost_dev@chezphil.org> wrote in message news:1291925453226@dmwebmail.dmwebmail.chezphil.org...
Christian Henning wrote:
This would assume that both png reader and writer have some bugs in common.
No it doesn't. Imagine a bug in the reader that caused the data to be all 0.
To follow Lubomir in giving Christian more support, the 'clear-cut' "no it doesn't" seems (even to me :) a bit too harsh as Christian did admit that the test is not perfect and, statistically speaking (as he spoke of 'good indication'), he was not so far from truth (i.e. what is the probability of the reader reading all zeros and what of the reader and writer having a common bug...)...
My "imagine..." line was intended to represent the whole class of faults that would not be detected by this testing strategy. For example, the last bug I had in my PNG loader was that it lost the right-most pixel of odd-width images when loading into a 16-bit destination. This would not be detected by this read-write-read-compare approach. Regards, Phil.