From: Calculemus <calculemus1988@gmail.com>

Date: Sat, 28 Jul 2012 00:33:31 +0200

Message-ID: <CAOn8Oo-Fb7QCeFs4-PFRNpbMq3pdvMf_d9n+UsgCzHOAVdBV+Q@mail.gmail.com>

To: Dirk Schulze <dschulze@adobe.com>

Cc: Rik Cabanier <cabanier@gmail.com>, "steve@fenestra.com" <steve@fenestra.com>, "www-svg@w3.org" <www-svg@w3.org>

Received on Friday, 27 July 2012 22:33:59 UTC

Date: Sat, 28 Jul 2012 00:33:31 +0200

Message-ID: <CAOn8Oo-Fb7QCeFs4-PFRNpbMq3pdvMf_d9n+UsgCzHOAVdBV+Q@mail.gmail.com>

To: Dirk Schulze <dschulze@adobe.com>

Cc: Rik Cabanier <cabanier@gmail.com>, "steve@fenestra.com" <steve@fenestra.com>, "www-svg@w3.org" <www-svg@w3.org>

Rik I am debugging as you suggested, and I found a mismatch between the formula and Photoshop's results. A is top image and B is bottom image in the attachment. The blend mode I apply in Photoshop is Multiply, just to keep calculations easy. R and B components match, but for G I get different result with the formula: G = A*alpha_A*(1-alpha_B) + B*alpha_B*(1-alpha_A) + alpha_A*alpha_B*Multiply(A,B) = 0.75*0.75*0 + 0.75*1*0.25 + 0.75*0.75*0.75= 0.609375 and that is different than 157 for G in Photoshop which maps to 157/256=0.61328125 in range 0 to 1. So in summary, I get same results for R and B, and for alpha, but different for G.

- application/rar attachment: 2.rar

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