msdf-error-correction.org

default is mode=edge-priority, distance-check-mode=check-distance-at-edge

default = auto = auto-mixed = mixed

auto-fast is mode=edge-priority, dcm=do-not-check-distance

auto-fast = fast

auto-full is mode=edge-priority dcm=always-check-distance

auto-full = full

distance is mode=indiscriminate, dcm = do-not-check-distance

distance = distance-fast = indiscriminate = indiscriminate-fast

distance-full is mode=indiscriminate, dcm = always-check-distance

distance-full = indiscriminate-full

edge-fast is mode=edge-only, dcm=do-not-check-distance

edge-full is mode=edge-only, dcm=always-check-distance

edge-full = edge

init

if correction mode is edge-priority

mark 4 samples of cell containing a corner of shape as ‘protected’

for each pair of adjacent samples:

(horizontal, vertical, or diagonal pairs)

if sum of pseudodistances at sample is less than distance between samples

for each channel

determine if channel contributes to an edge between those texels

find position where specified channel of those texels, crosses 0if it is between the 2 texels:interpolate the texels at that positionchannel contributes to edge iff median of interpolated value is in specified channel of interpolated value

for each sample in pair

if a channel that contributes to an edge is not the median of that sample:

mark the sample as protected

if config is edge-only

mark all samples as ‘protected’

if

distance check mode is do-not-check-distance

or

distance check mode is check-distance-at-edge and correction mode is edge-only

run find-error (below) with base artifact classifier

if distance check mode is check-distance-at-edge

mark all samples as ‘protected’

if distance check mode is always-check-distance or check-distance-at-edge

if overlap check is supported

run find-errors w/ shape distance checker w/ overlapping contour combiner

if overlap check not supported

run find errors w/ shape distance checker w/ simple contour combiner

find error

at each sample, mark it as ‘error’ if it has artifacts with adjacent sample

(check all 8 adjacent samples that are in bounds for sdf)

horizontal/vertical:

if texel is further from edge of pair:

return true if for any pair of channels:

(RG,GB,RB)

at point between samples where 2 channels have same value:

ignoring cases where that point is eactly at a sample (or within some epsilon)

for base artifact checker:eithermedian interpolated at that point has different sign from sample mediansor sample being tested isn’t protected and is not between sample mediansand interpolated median is not a plausible distance from sample medians (a distance field sampled every N units can at most change by N between adjacent samples. So for a point between two samples,if it is T units from first sample, the interpolated distance at that point must be within T of first sample and N-T from 2nd)

(not exact, allow within N% of exact distance)

for distance checker w/ contour combiner:run base checker, and if it got to 3rd test and distance was plausible:calculate exact distance to shape at that pointcalculate interpolated distance from msdfcalculate interpolated distance if sample were flattenedmark sample if new distance is closer to exact distance

diagonal

same as horiz/vert, except:

bilinear interpolation, so need to solve quadratic to find point (and possibly 2 points

also check for a local extreme of each channel of the pair being tested along the diagonal, and run artifact check routine with the interpolated value at that extreme instead of one of corresponding sample

(ex. if samples are at 0 and 1, test point is at 0.5, channel maximum is 0.7, check with 0 and 0.7 instead of 0 and 1)

apply error correction

for every sample

if marked ‘error’, set all channels to median