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Implement grayscale bilateral filter

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This commit is contained in:
Ben Olden-Cooligan 2024-03-03 10:31:31 -08:00
parent 1bafd46ac0
commit 22f48b27e0
2 changed files with 119 additions and 21 deletions
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129
NAPS2.Images/Bitwise/BilateralFilterOp.cs
View File

@ -20,11 +20,14 @@ public class BilateralFilterOp : BinaryBitwiseImageOp
protected override void PerformCore(BitwiseImageData src, BitwiseImageData dst, int partStart, int partEnd)
{
// TODO: Implement grayscale?
if (src.bytesPerPixel is 3 or 4 && dst.bytesPerPixel is 3 or 4)
{
PerformRgba(src, dst, partStart, partEnd);
}
else if (src.bytesPerPixel == 1 && dst.bytesPerPixel == 1)
{
PerformGray(src, dst, partStart, partEnd);
}
else
{
throw new InvalidOperationException("Unsupported pixel format");
@ -36,25 +39,8 @@ public class BilateralFilterOp : BinaryBitwiseImageOp
bool copyAlpha = src.hasAlpha && dst.hasAlpha;
const int s = FILTER_SIZE / 2;
var filter = new int[FILTER_SIZE * FILTER_SIZE];
for (int filterX = 0; filterX < FILTER_SIZE; filterX++)
{
for (int filterY = 0; filterY < FILTER_SIZE; filterY++)
{
int dx = filterX - s;
int dy = filterY - s;
var dmax = Math.Sqrt(2 * s * s);
var d = Math.Sqrt(dx * dx + dy * dy) / dmax;
filter[filterX + filterY * FILTER_SIZE] = (int)((1 - d) * 256);
}
}
var diffWeights = new int[256 * 3 * 2];
for (int i = 0; i < COLOR_DIST_MAX * 3; i++)
{
diffWeights[256 * 3 + i] = COLOR_DIST_MAX - i / 3;
diffWeights[256 * 3 - i] = COLOR_DIST_MAX - i / 3;
}
var filter = BuildFilter();
var diffWeights = BuildRgbaDiffWeights();
for (int i = partStart; i < partEnd; i++)
{
@ -81,7 +67,8 @@ public class BilateralFilterOp : BinaryBitwiseImageOp
byte nextR = *(nextPixel + src.rOff);
byte nextG = *(nextPixel + src.gOff);
byte nextB = *(nextPixel + src.bOff);
if (prevR == 255 && prevG == 255 && prevB == 255 && nextR == 255 && nextG == 255 && nextB == 255)
if (prevR == 255 && prevG == 255 && prevB == 255 && nextR == 255 && nextG == 255 &&
nextB == 255)
{
skipPixel = true;
}
@ -127,4 +114,104 @@ public class BilateralFilterOp : BinaryBitwiseImageOp
}
}
}
private unsafe void PerformGray(BitwiseImageData src, BitwiseImageData dst, int partStart, int partEnd)
{
const int s = FILTER_SIZE / 2;
var filter = BuildFilter();
var diffWeights = BuildGrayDiffWeights();
for (int i = partStart; i < partEnd; i++)
{
var srcRow = src.ptr + src.stride * i;
var dstRow = dst.ptr + dst.stride * i;
for (int j = 0; j < src.w; j++)
{
var srcPixel = srcRow + j * src.bytesPerPixel;
var dstPixel = dstRow + j * dst.bytesPerPixel;
int lum = *srcPixel;
if (j > s && j < src.w - s && i > s && i < src.h - s)
{
bool skipPixel = false;
if (lum == 255)
{
var prevPixel = src.ptr + src.stride * i + src.bytesPerPixel * j - 1;
var nextPixel = src.ptr + src.stride * i + src.bytesPerPixel * j + 1;
byte prev = *prevPixel;
byte next = *nextPixel;
if (prev == 255 && next == 255)
{
skipPixel = true;
}
}
if (!skipPixel)
{
int lumTotal = 0;
int weightTotal = 0;
for (int filterX = 0; filterX < FILTER_SIZE; filterX++)
{
for (int filterY = 0; filterY < FILTER_SIZE; filterY++)
{
int imageX = j - s + filterX;
int imageY = i - s + filterY;
var pixel = src.ptr + src.stride * imageY + src.bytesPerPixel * imageX;
var lum2 = *pixel;
var diff = lum - lum2 + 256;
var weight = filter[filterX + filterY * FILTER_SIZE] * diffWeights[diff];
weightTotal += weight;
lumTotal += lum2 * weight;
}
}
lum = lumTotal / weightTotal;
}
}
*dstPixel = (byte) lum;
}
}
}
private static int[] BuildFilter()
{
const int s = FILTER_SIZE / 2;
var filter = new int[FILTER_SIZE * FILTER_SIZE];
for (int filterX = 0; filterX < FILTER_SIZE; filterX++)
{
for (int filterY = 0; filterY < FILTER_SIZE; filterY++)
{
int dx = filterX - s;
int dy = filterY - s;
var dmax = Math.Sqrt(2 * s * s);
var d = Math.Sqrt(dx * dx + dy * dy) / dmax;
filter[filterX + filterY * FILTER_SIZE] = (int) ((1 - d) * 256);
}
}
return filter;
}
private static int[] BuildRgbaDiffWeights()
{
var diffWeights = new int[256 * 3 * 2];
for (int i = 0; i < COLOR_DIST_MAX * 3; i++)
{
diffWeights[256 * 3 + i] = COLOR_DIST_MAX - i / 3;
diffWeights[256 * 3 - i] = COLOR_DIST_MAX - i / 3;
}
return diffWeights;
}
private static int[] BuildGrayDiffWeights()
{
var diffWeights = new int[256 * 2];
for (int i = 0; i < COLOR_DIST_MAX; i++)
{
diffWeights[256 + i] = COLOR_DIST_MAX - i;
diffWeights[256 - i] = COLOR_DIST_MAX - i;
}
return diffWeights;
}
}

11
NAPS2.Sdk.Tests/Images/BitwisePerfTests.cs
View File

@ -163,6 +163,17 @@ public class BitwisePerfTests : ContextualTests
new BilateralFilterOp().Perform(image, image2);
}
[Fact]
public void BilateralFilterGray()
{
// Using a smaller size as sharpening is super slow
using var image = CreateAndFill(ImagePixelFormat.Gray8, SIZE / 4);
using var image2 = CreateAndFill(ImagePixelFormat.Gray8, SIZE / 4);
using var _ = Timer();
new BilateralFilterOp().Perform(image, image2);
}
[Fact]
public void LogicalPixelFormat()
{