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// tslint:disable:prefer-for-of
import { contrastRatio } from "./color-converters";
import { ColorInterpolationSpace, interpolateByColorSpace } from "./color-interpolation";
import { ColorRGBA64 } from "./color-rgba-64";
export interface ColorScaleStop {
color: ColorRGBA64;
position: number;
}
export class ColorScale {
public static createBalancedColorScale(colors: ColorRGBA64[]): ColorScale {
if (colors == null || colors.length === 0) {
throw new Error("The colors argument must be non-empty");
}
const stops: ColorScaleStop[] = new Array(colors.length);
for (let i: number = 0; i < colors.length; i++) {
// Special case first and last in order to avoid floating point jaggies
if (i === 0) {
stops[i] = { color: colors[i], position: 0 };
} else if (i === colors.length - 1) {
stops[i] = { color: colors[i], position: 1 };
} else {
stops[i] = {
color: colors[i],
position: i * (1 / (colors.length - 1)),
};
}
}
return new ColorScale(stops);
}
constructor(stops: ColorScaleStop[]) {
if (stops == null || stops.length === 0) {
throw new Error("The stops argument must be non-empty");
} else {
this.stops = stops;
}
}
private readonly stops: ColorScaleStop[];
public getColor(
position: number,
interpolationMode: ColorInterpolationSpace = ColorInterpolationSpace.RGB
): ColorRGBA64 {
if (this.stops.length === 1) {
return this.stops[0].color;
} else if (position <= 0) {
return this.stops[0].color;
} else if (position >= 1) {
return this.stops[this.stops.length - 1].color;
}
let lowerIndex: number = 0;
for (let i: number = 0; i < this.stops.length; i++) {
if (this.stops[i].position <= position) {
lowerIndex = i;
}
}
let upperIndex: number = lowerIndex + 1;
if (upperIndex >= this.stops.length) {
upperIndex = this.stops.length - 1;
}
const scalePosition: number =
(position - this.stops[lowerIndex].position) *
(1.0 / (this.stops[upperIndex].position - this.stops[lowerIndex].position));
return interpolateByColorSpace(
scalePosition,
interpolationMode,
this.stops[lowerIndex].color,
this.stops[upperIndex].color
);
}
public trim(
lowerBound: number,
upperBound: number,
interpolationMode: ColorInterpolationSpace = ColorInterpolationSpace.RGB
): ColorScale {
if (lowerBound < 0 || upperBound > 1 || upperBound < lowerBound) {
throw new Error("Invalid bounds");
}
if (lowerBound === upperBound) {
return new ColorScale([
{ color: this.getColor(lowerBound, interpolationMode), position: 0 },
]);
}
const containedStops: ColorScaleStop[] = [];
for (let i: number = 0; i < this.stops.length; i++) {
if (
this.stops[i].position >= lowerBound &&
this.stops[i].position <= upperBound
) {
containedStops.push(this.stops[i]);
}
}
if (containedStops.length === 0) {
return new ColorScale([
{ color: this.getColor(lowerBound), position: lowerBound },
{ color: this.getColor(upperBound), position: upperBound },
]);
}
if (containedStops[0].position !== lowerBound) {
containedStops.unshift({
color: this.getColor(lowerBound),
position: lowerBound,
});
}
if (containedStops[containedStops.length - 1].position !== upperBound) {
containedStops.push({
color: this.getColor(upperBound),
position: upperBound,
});
}
const range: number = upperBound - lowerBound;
const finalStops: ColorScaleStop[] = new Array(containedStops.length);
for (let i: number = 0; i < containedStops.length; i++) {
finalStops[i] = {
color: containedStops[i].color,
position: (containedStops[i].position - lowerBound) / range,
};
}
return new ColorScale(finalStops);
}
public findNextColor(
position: number,
contrast: number,
searchDown: boolean = false,
interpolationMode: ColorInterpolationSpace = ColorInterpolationSpace.RGB,
contrastErrorMargin: number = 0.005,
maxSearchIterations: number = 32
): number {
if (isNaN(position) || position <= 0) {
position = 0;
} else if (position >= 1) {
position = 1;
}
const startingColor: ColorRGBA64 = this.getColor(position, interpolationMode);
const finalPosition: number = searchDown ? 0 : 1;
const finalColor: ColorRGBA64 = this.getColor(finalPosition, interpolationMode);
const finalContrast: number = contrastRatio(startingColor, finalColor);
if (finalContrast <= contrast) {
return finalPosition;
}
let testRangeMin: number = searchDown ? 0 : position;
let testRangeMax: number = searchDown ? position : 0;
let mid: number = finalPosition;
let iterations: number = 0;
while (iterations <= maxSearchIterations) {
mid = Math.abs(testRangeMax - testRangeMin) / 2 + testRangeMin;
const midColor: ColorRGBA64 = this.getColor(mid, interpolationMode);
const midContrast: number = contrastRatio(startingColor, midColor);
if (Math.abs(midContrast - contrast) <= contrastErrorMargin) {
return mid;
} else if (midContrast > contrast) {
if (searchDown) {
testRangeMin = mid;
} else {
testRangeMax = mid;
}
} else {
if (searchDown) {
testRangeMax = mid;
} else {
testRangeMin = mid;
}
}
iterations++;
}
return mid;
}
public clone(): ColorScale {
const newStops: ColorScaleStop[] = new Array(this.stops.length);
for (let i: number = 0; i < newStops.length; i++) {
newStops[i] = {
color: this.stops[i].color,
position: this.stops[i].position,
};
}
return new ColorScale(newStops);
}
}
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