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Better smoothing of resolution and center constraints

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Previously the formula for the resolution constraint allowed going way past
the minimum zoom.
Also adjusted the center constraint to avoid a zigzag effect when going out
of resolution bounds.
This commit is contained in:
Olivier Guyot
2019-02-25 23:12:39 +01:00
parent f67baa0dc0
commit 447266cbe8
2 changed files with 24 additions and 9 deletions
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src/ol/resolutionconstraint.js
+8 -3
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@@ -27,6 +27,10 @@ function getViewportClampedResolution(resolution, maxExtent, viewportSize) {
/**
* Returns a modified resolution to be between maxResolution and minResolution while
* still allowing the value to be slightly out of bounds.
* Note: the computation is based on the logarithm function (ln):
* - at 1, ln(x) is 0
* - above 1, ln(x) keeps increasing but at a much slower pace than x
* The final result is clamped to prevent getting too far away from bounds.
* @param {number} resolution Resolution.
* @param {number} maxResolution Max resolution.
* @param {number} minResolution Min resolution.
@@ -34,13 +38,14 @@ function getViewportClampedResolution(resolution, maxExtent, viewportSize) {
*/
function getSmoothClampedResolution(resolution, maxResolution, minResolution) {
let result = Math.min(resolution, maxResolution);
const ratio = 50;
result *= Math.log(Math.max(1, resolution / maxResolution)) * 0.1 + 1;
result *= Math.log(1 + ratio * Math.max(0, resolution / maxResolution - 1)) / ratio + 1;
if (minResolution) {
result = Math.max(result, minResolution);
result /= Math.log(Math.max(1, minResolution / resolution)) * 0.1 + 1;
result /= Math.log(1 + ratio * Math.max(0, minResolution / resolution - 1)) / ratio + 1;
}
return result;
return clamp(result, minResolution / 2, maxResolution * 2);
}
/**