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This is one of those internet myths that just persists.

According to your formula, this image and this one ought to approach 2.0. They are to all intents and purposes identical.

The actual result:

C:\test>jimagezipcmp.pl adding: 1.png (160 bytes security) (deflated 90%) adding: 2.png (160 bytes security) (deflated 89%) adding: 1.png (160 bytes security) (deflated 90%) adding: 2.png (160 bytes security) (deflated 89%) 1.0272952853598

Try it yourself:

#! perl -slw use strict; use GD; sub rgb2n { unpack 'N', pack 'CCCC', 0, @_ } for my $n ( 1, 2 ) { my $im1 = GD::Image->new( 600, 400, 1 ); $im1->filledRectangle( 0, 0, 600, 400, rgb2n( 255, 255, 255 ) ); $im1->filledRectangle( 100, 100, 500, 300, rgb2n( 255 - $n, 0, 0 ) + ); open O, '>:raw', $n . '.png' or die $!; print O $im1->png; close O; } system q[zip 1.zip 1.png]; system q[zip 2.zip 2.png]; system q[zip 3.zip 1.png 2.png]; my $size1 = -s '1.zip'; my $size2 = -s '2.zip'; my $size3 = -s '3.zip'; print +( $size1 + $size2 ) / $size3;

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^2: Can i Compare two images in perl ? (It's a myth!) by BrowserUk
in thread Can i Compare two images in perl ? by deep3101

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