static void no_interpolation(const ImageData *image, DBL xcoor, DBL ycoor, RGBFTColour& colour, int *index, bool premul)
{
int iycoor, ixcoor;
if(image->Once_Flag)
{
// image is to be seen only once, so when taking samples for interpolation
// coordinates should not wrap around; instead, take the samples from the nearest
// pixel right at the edge of the image
if(xcoor < 0.0)
ixcoor = 0;
else if(xcoor >= (DBL)image->iwidth)
ixcoor = image->iwidth - 1;
else
ixcoor = (int)xcoor;
if(ycoor < 0.0)
iycoor = 0;
else if(ycoor >= (DBL)image->iheight)
iycoor = image->iheight - 1;
else
iycoor = (int)ycoor;
}
else
{
// image is to be repeated, so when taking samples for interpolation
// have coordinates wrap around
ixcoor = (int)wrap(xcoor, (DBL)image->iwidth);
iycoor = (int)wrap(ycoor, (DBL)image->iheight);
}
image->data->GetRGBFTValue(ixcoor, iycoor, colour, premul);
if(image->data->IsIndexed() == false)
{
*index = -1;
if (image->AllTransmitLegacyMode)
{
// Legacy versions applied "transmit/filter all" before interpolation,
// and with little respect to an image's inherent alpha information.
colour.transm() += image->AllTransmit;
colour.filter() += image->AllFilter;
}
}
else
*index = image->data->GetIndexedValue(ixcoor, iycoor);
}
void image_colour_at(const ImageData *image, DBL xcoor, DBL ycoor, RGBFTColour& colour, int *index, bool premul)
{
*index = -1;
bool doProperTransmitAll = image->data->HasTransparency() &&
!image->AllTransmitLegacyMode &&
!image->data->IsIndexed() && ( (image->AllTransmit != 0.0) || (image->AllFilter != 0.0) );
// If either source or destination uses premultiplied alpha, make sure interpolation is done in premultiplied space
// as it makes the mathematical operations cleaner -- unless the alpha channel is modulated by "transmit all" or
// "filter all", in which case we prefer non-premultiplied space.
bool getPremul = doProperTransmitAll ? (premul && image->data->IsPremultiplied()) :
(premul || image->data->IsPremultiplied());
switch(image->Interpolation_Type)
{
case NO_INTERPOLATION:
no_interpolation(image, xcoor, ycoor, colour, index, getPremul);
break;
case BICUBIC:
InterpolateBicubic(image, xcoor, ycoor, colour, index, getPremul);
break;
default:
Interp(image, xcoor, ycoor, colour, index, getPremul);
break;
}
bool havePremul = getPremul;
if (!premul && havePremul)
{
// We fetched premultiplied data, but caller expects it non-premultiplied, so we need to fix that.
// As "transmit/filter all" handling also works best on non-premultiplied data, we're doing this now.
AlphaUnPremultiply(colour.rgb(), colour.FTtoA());
havePremul = false;
}
if (doProperTransmitAll)
{
COLC imageAlpha = colour.FTtoA();
if (imageAlpha != 0.0) // No need to apply "filter/transmit all" if the image is fully transparent here anyway.
{
colour.transm() += image->AllTransmit * imageAlpha;
colour.filter() += image->AllFilter * imageAlpha;
if (havePremul)
{
// We have premultiplied data here, and the caller expects it to stay that way (otherwise we'd already
// have converted to non-premultiplied by now), so we need to fix the premultiplication of the colour
// according to our modifications to the transparency components.
COLC alphaCorrection = colour.FTtoA() / imageAlpha;
AlphaPremultiply(colour.rgb(), alphaCorrection);
}
}
}
if (premul && !havePremul)
{
// We have non-premultiplied data here, but caller expects it premultiplied, so we need to fix that
// As "transmit/filter all" handling works best on non-premultiplied data, we haven't done this earlier.
AlphaPremultiply(colour.rgb(), colour.FTtoA());
}
}