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Just draw everything on pixel boundaries. Browsers just get the

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difficult cases wrong.
This commit is contained in:
philip
2020-05-17 00:13:40 +00:00
parent a4a1c25f2e
commit c1949a28f0
1 changed files with 15 additions and 21 deletions
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36
src/ol/reproj.js
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@@ -298,12 +298,13 @@ export function render(
y1 = source[1][1]; y1 = source[1][1];
let x2 = source[2][0], let x2 = source[2][0],
y2 = source[2][1]; y2 = source[2][1];
const u0 = (target[0][0] - targetTopLeft[0]) / targetResolution; // Make sure that everything is on pixel boundaries
const v0 = -(target[0][1] - targetTopLeft[1]) / targetResolution; const u0 = pixelRound((target[0][0] - targetTopLeft[0]) / targetResolution);
const u1 = (target[1][0] - targetTopLeft[0]) / targetResolution; const v0 = pixelRound(-(target[0][1] - targetTopLeft[1]) / targetResolution);
const v1 = -(target[1][1] - targetTopLeft[1]) / targetResolution; const u1 = pixelRound((target[1][0] - targetTopLeft[0]) / targetResolution);
const u2 = (target[2][0] - targetTopLeft[0]) / targetResolution; const v1 = pixelRound(-(target[1][1] - targetTopLeft[1]) / targetResolution);
const v2 = -(target[2][1] - targetTopLeft[1]) / targetResolution; const u2 = pixelRound((target[2][0] - targetTopLeft[0]) / targetResolution);
const v2 = pixelRound(-(target[2][1] - targetTopLeft[1]) / targetResolution);
// Shift all the source points to improve numerical stability // Shift all the source points to improve numerical stability
// of all the subsequent calculations. The [x0, y0] is used here. // of all the subsequent calculations. The [x0, y0] is used here.
@@ -335,35 +336,28 @@ export function render(
isBrokenDiagonalRendering() || isBrokenDiagonalRendering() ||
opt_contextOptions === IMAGE_SMOOTHING_DISABLED opt_contextOptions === IMAGE_SMOOTHING_DISABLED
) { ) {
// Make sure that everything is on pixel boundaries
const u0r = pixelRound(u0);
const v0r = pixelRound(v0);
const u1r = pixelRound(u1);
const v1r = pixelRound(v1);
const u2r = pixelRound(u2);
const v2r = pixelRound(v2);
// Make sure that all lines are horizontal or vertical // Make sure that all lines are horizontal or vertical
context.moveTo(u1r, v1r); context.moveTo(u1, v1);
// This is the diagonal line. Do it in 4 steps // This is the diagonal line. Do it in 4 steps
const steps = 4; const steps = 4;
const ud = u0r - u1r; const ud = u0 - u1;
const vd = v0r - v1r; const vd = v0 - v1;
for (let step = 0; step < steps; step++) { for (let step = 0; step < steps; step++) {
// Go horizontally // Go horizontally
context.lineTo( context.lineTo(
u1r + pixelRound(((step + 1) * ud) / steps), u1 + pixelRound(((step + 1) * ud) / steps),
v1r + pixelRound((step * vd) / (steps - 1)) v1 + pixelRound((step * vd) / (steps - 1))
); );
// Go vertically // Go vertically
if (step != steps - 1) { if (step != steps - 1) {
context.lineTo( context.lineTo(
u1r + pixelRound(((step + 1) * ud) / steps), u1 + pixelRound(((step + 1) * ud) / steps),
v1r + pixelRound(((step + 1) * vd) / (steps - 1)) v1 + pixelRound(((step + 1) * vd) / (steps - 1))
); );
} }
} }
// We are almost at u0r, v0r // We are almost at u0r, v0r
context.lineTo(u2r, v2r); context.lineTo(u2, v2);
} else { } else {
context.moveTo(u1, v1); context.moveTo(u1, v1);
context.lineTo(u0, v0); context.lineTo(u0, v0);