diff options
| -rw-r--r-- | editor/pamcomp.c | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/editor/pamcomp.c b/editor/pamcomp.c index 53e5f252..332acac3 100644 --- a/editor/pamcomp.c +++ b/editor/pamcomp.c @@ -437,6 +437,13 @@ computeOverlayPosition(int const underCols, overlaying images are plastic slides and we taped them together to make a composed plastic slide, the calculations go as follows. + U means color of underlay pixel + O means color of overlay pixel + C means color of composed pixel + X is a variable, standing for U, O, or C + X_T means transparency of the X pixel + X_O means opacity of the X pixel + Opacity and transparency are fractions in [0,1] and are complements: X_T = 1 - X_O @@ -480,23 +487,24 @@ static sample composeComponents(sample const compA, sample const compB, float const distrib, - float const aFactor, + float const bFactor, float const composedFactor, sample const maxval, enum sampleScale const sampleScale) { /*---------------------------------------------------------------------------- Compose a single color component of each of two pixels, with 'distrib' being the fraction of 'compA' in the result, 1-distrib the fraction of 'compB'. - Note that this does not apply to an opacity component. + + Note that this function is not useful for an opacity component. 'sampleScale' tells in what domain the 'distrib' fraction applies: brightness or light intensity (gamma-adjusted or not). - 'aFactor' is a factor in [0,1] to apply to 'compA' first. + 'bFactor' is a factor in [0,1] to apply to 'compB' first. 'composedFactor' is a factor to apply to the result. - See above for explanation of why 'aFactor' and 'composedFactor' are + See above for explanation of why 'bFactor' and 'composedFactor' are useful. The inputs and result are based on a maxval of 'maxval'. @@ -507,22 +515,22 @@ composeComponents(sample const compA, -----------------------------------------------------------------------------*/ sample retval; - if (fabs(distrib) > .999 && aFactor > .999 && composedFactor > .999) + if (fabs(distrib) > .999 && bFactor > .999 && composedFactor > .999) /* Fast path for common case */ retval = compA; else { if (sampleScale == INTENSITY_SAMPLE) { sample const mix = - ROUNDU(compA * aFactor * distrib + compB * (1.0 - distrib)); + ROUNDU(compA * distrib + compB * bFactor *(1.0 - distrib)); retval = MIN(maxval, MAX(0, mix)); } else { float const compANormalized = (float)compA/maxval; float const compBNormalized = (float)compB/maxval; float const compALinear = pm_ungamma709(compANormalized); float const compBLinear = pm_ungamma709(compBNormalized); - float const compALinearAdj = compALinear * aFactor; + float const compBLinearAdj = compBLinear * bFactor; float const mix = - compALinearAdj * distrib + compBLinear * (1.0 - distrib) + compALinear * distrib + compBLinearAdj * (1.0 - distrib) * composedFactor; sample const sampleValue = ROUNDU(pm_gamma709(mix) * maxval); retval = MIN(maxval, MAX(0, sampleValue)); |