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implement dithering!
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@micycle1
micycle1 committed Dec 30, 2024
1 parent ddad84a commit e8c1ccb
Showing 1 changed file with 86 additions and 49 deletions.
135 changes: 86 additions & 49 deletions src/main/micycle/peasygradients/PeasyGradients.java
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ public final class PeasyGradients {
private static final double HALF_PI = (0.5 * Math.PI);
private static final double INV_TWO_PI = 1 / TWO_PI;
private static final double THREE_QRTR_PI = (0.75 * Math.PI);
private static final double DEFAULT_DITHER = 0.015;

private static final ExecutorService THREAD_POOL;

Expand Down Expand Up @@ -105,6 +106,8 @@ public final class PeasyGradients {
private int renderOffsetX, renderOffsetY; // gradient region offsets (usually 0, 0)
private double scaleY, scaleX;

private double ditherStrength = DEFAULT_DITHER;

/**
* Number of horizontal strips the plane is paritioned into for threaded
* rendering
Expand Down Expand Up @@ -233,9 +236,39 @@ public void setNoiseSeed(int seed) {
fastNoiseLite.SetSeed(seed);
}

/**
* Sets the dithering strength.
* <p>
* Dithering helps to reduce the visibility of color-banding within gradients.
* It breaks up the noticeable banding-edges and replace them with less
* noticeable noise. The strength parameter defines the maximum amount by which
* a color at read at location t may deviate from its position along the 1D
* gradient spectrum.
*
* @param strength A value >=0. Default = 0.015 (akin to a max deviation of 1.5%
* from the colorstop)
*/

/**
* Adjusts the dithering strength to reduce color banding in gradients.
* <p>
* Dithering disperses the visible color-banding by replacing sharp banding
* edges with subtle noise. The 'strength' parameter specifies the maximum
* permissible deviation for a color at a given position from its expected
* position in the underlying 1D gradient spectrum, expressed as a fraction.
*
* @param strength A non-negative value specifying the deviation fraction.
* Default is 0.015 (1.5% deviation).
*/
public void setDitherStrength(double strength) {
ditherStrength = strength;
}

/**
* Restricts any and all rendered gradients to render in at most n colors
* (a.k.a. posterisation).
* <p>
* Note that applying posterisation will disable dithering.
*
* @param n max number of colors
* @see #clearPosterisation()
Expand All @@ -245,15 +278,21 @@ public void posterise(int n) {
if (n != gradientCacheSize) {
gradientCacheSize = n;
gradientCache = new int[gradientCacheSize];
ditherStrength = 0;
}
}

/**
* Clears any user-defined color posterisation setting.
* <p>
* Note clearing posterisation restores dithering back to its default strength.
*
* @see #posterise(int)
*/
public void clearPosterisation() {
if (ditherStrength == 0) {
ditherStrength = DEFAULT_DITHER;
}
setRenderTarget(gradientPG, renderOffsetX, renderOffsetY, renderWidth, renderHeight);
}

Expand Down Expand Up @@ -876,7 +915,40 @@ private void makeThreadPool(Gradient gradient, final int partitionsY, final Clas
e.printStackTrace();
}
// else, the given args probably don't match the thread class args
}

/**
* @return an appropriate index into the gradient color LUT
*/
private int clampAndDither(double t, int x, int y) {
/*
* Clamp first, then dither (i.e. no point dithering values >1 if they are later
* clamped back to 1.0.
*/
t = (t < 0) ? 0 : (t > 1 ? 1 : t); // clamp between 0...1

if (ditherStrength > 0) {
double d = interleavedGradientNoise(x, y);
t += d;
// reclamp
if (t < 0) {
t = 0;
}
}

// if t==1, index would be out of bounds, so take min()
int stepInt = Math.min((int) (t * gradientCacheSize), gradientCacheSize - 1);

return stepInt;
}

private double interleavedGradientNoise(final int x, final int y) {
// http://www.iryoku.com/next-generation-post-processing-in-call-of-duty-advanced-warfare
// https://bartwronski.com/2016/10/30/dithering-part-three-real-world-2d-quantization-dithering/
final double v = 52.9829189 * (0.06711056 * x + 0.00583715 * y);
double n = (v - Math.floor(v)); // take fractional part (range of 1)
n = n * 2 - 1; // adjust range from [0,1] to [-1,1]
return n * ditherStrength; // scale output
}

/**
Expand Down Expand Up @@ -932,10 +1004,10 @@ public Boolean call() {
double xOff = 0; // set partition x offset to correct amount
for (int x = 0; x < renderWidth; x++) {
double step = (opXod + xOff) * odSqInverse; // get position of point on 1D gradient and normalise
step = (step < 0) ? 0 : (step > 1 ? 1 : step); // clamp between 0...1
int stepInt = Math.min((int) (step * gradientCacheSize), gradientCacheSize - 1);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
xOff += odX * scaleX;

int stepInt = clampAndDither(step, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}

Expand Down Expand Up @@ -969,11 +1041,7 @@ public Boolean call() {
double distSq = run + rise;
double dist = zoom * distSq;

if (dist > 1) { // clamp to a high of 1
dist = 1;
}

int stepInt = Math.min((int) (dist * gradientCacheSize), gradientCacheSize - 1);
int stepInt = clampAndDither(dist, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1008,14 +1076,7 @@ public Boolean call() {
t *= INV_TWO_PI; // normalise
t -= Math.floor(t); // modulo

// Math.round(t * (gradientCacheSize - 1));
// t = (t < 0) ? 0 : (t >= 1 ? 1 - 1e-10 : t); // clamp between 0 and slightly less than 1
if (t > 1) { // clamp to a high of 1
t = 1;
}

int stepInt = Math.min((int) (t * gradientCacheSize), gradientCacheSize - 1);

int stepInt = clampAndDither(t, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];

}
Expand Down Expand Up @@ -1071,7 +1132,7 @@ public Boolean call() throws Exception {
t *= INV_TWO_PI; // normalise
t -= Math.floor(t); // modulo

int stepInt = Math.min((int) (t * gradientCacheSize), gradientCacheSize - 1);
int stepInt = clampAndDither(t, x, y);

gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
Expand Down Expand Up @@ -1115,12 +1176,7 @@ public Boolean call() {

double dist = polygonRatio * pointDistance;

if (dist > 1) { // clamp to a high of 1
dist = 1;
}

final int stepInt = Math.min((int) (dist * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(dist, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1156,12 +1212,7 @@ public Boolean call() {

double dist = Math.min(Math.abs(newYpos - renderMidpointY), Math.abs(newXpos - renderMidpointX)) / denominator; // min

if (dist > 1) { // clamp to a high of 1
dist = 1;
}

final int stepInt = Math.min((int) (dist * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(dist, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1197,12 +1248,7 @@ public Boolean call() {

double dist = Math.max(Math.abs(newYpos - renderMidpointY), Math.abs(newXpos - renderMidpointX)) / denominator; // max

if (dist > 1) { // clamp to a high of 1
dist = 1;
}

final int stepInt = Math.min((int) (dist * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(dist, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1235,8 +1281,7 @@ public Boolean call() {

double step = fastNoiseLite.getSimplexNoiseFast((float) newXpos, (float) newYpos); // call custom method

final int stepInt = Math.min((int) (step * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(step, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1268,8 +1313,7 @@ public Boolean call() {

double step = uniformNoise.uniformNoise(scale * newXpos, newYpos * scale, z);

final int stepInt = Math.min((int) (step * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(step, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1306,8 +1350,7 @@ public Boolean call() {
double step = fastNoiseLite.GetNoise((float) newXpos, (float) newYpos);
step = ((step - min) * (maxMinDenom)); // scale to 0...1

final int stepInt = Math.min((int) (step * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(step, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1358,8 +1401,7 @@ public Boolean call() {
step = 1;
}

int stepInt = Math.min((int) (step * gradientCacheSize), gradientCacheSize - 1);

int stepInt = clampAndDither(step, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down Expand Up @@ -1419,12 +1461,7 @@ public Boolean call() {
double dist = Math.sqrt((yDist + xDist + pinch) * (z * z + roundness)) * denominator; // cos(atan(x)) === sqrt(z * z +
// 1)

if (dist > 1) { // clamp to a high of 1
dist = 1;
}

final int stepInt = Math.min((int) (dist * gradientCacheSize), gradientCacheSize - 1);

final int stepInt = clampAndDither(dist, x, y);
gradientPG.pixels[pixel++] = gradientCache[stepInt];
}
}
Expand Down

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