diff options
| -rw-r--r-- | editor/pamscale.c | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/editor/pamscale.c b/editor/pamscale.c index 0a2e955f..1b3ab8f0 100644 --- a/editor/pamscale.c +++ b/editor/pamscale.c @@ -1025,12 +1025,12 @@ createWeightList(unsigned int const targetPos, row. Assume 'filter' is a triangle function -- 1 at 0, sloping down to 0 at -1 and 1. - Now assume that the scale factor is 2 -- the target image will be - twice the size of the source image. That means the two-pixel-wide - window of the source row that affects Column 5 of the target row - (centered at target position 5.5) goes from position 1.75 to - 3.75, centered at 2.75. That means the window covers 1/4 of - Column 1, all of Column 2, and 3/4 of Column 3 of the source row. + Now assume that the scale factor is 2 -- the target image will be twice the + size of the source image. That means the two-pixel-wide window of the + source row that affects Column 5 of the target row, which is centered at + target position 5.5, is centered at source position 5.5/2 = 2.75. So it + goes from source position 1.75 to 3.75. That means the window covers 1/4 + of Column 1, all of Column 2, and 3/4 of Column 3 of the source row. We want to calculate 3 weights, one to be applied to each source pixel in computing the target pixel. Ideally, we would compute the average @@ -1043,19 +1043,19 @@ createWeightList(unsigned int const targetPos, -.875 from the center of the window, we assume a constant function value of triangle(-.875), which equals .125. For the 2.00-3.00 region, we get triangle(-.25) = .75. For the 3.00-3.75 region, we - get triangle(.125) = .875. So the weights for the 3 regions, which + get triangle(.625) = .375. So the weights for the 3 regions, which we get by multiplying this constant function value by the width of the region and normalizing so they add up to 1 are: - Source Column 1: .125*.25 / 1.4375 = .022 - Source Column 2: .75*1.00 / 1.4375 = .521 - Source Column 3: .875*.75 / 1.4375 = .457 + Source Column 1: .125*.25 / 1.0625 = .029 + Source Column 2: .75*1.00 / 1.0625 = .706 + Source Column 3: .375*.75 / 1.0625 = .265 These are the weights we return. Thus, if we assume that the source pixel 1 has value 10, source pixel 2 has value 20, and source pixel 3 has value 30, Caller would compute target pixel 5's value as - 10*.022 + 20*.521 + 30*.457 = 24 + 10*.029 + 20*.706 + 30*.265 = 22 -----------------------------------------------------------------------------*/ /* 'windowCenter', is the continuous position within the source of |