Smooth blur: replace O(N*r) box blur with O(N) sliding window box blur and scale intensity linearly from 1 to 40

This commit is contained in:
2026-07-06 18:45:12 +07:00
parent fe095304cc
commit 7e21d37ae2
@@ -1664,7 +1664,7 @@ class MainActivity : AppCompatActivity() {
if (!isAiSupported) {
if (blurIntensity > 0f) {
val radius = (25 * blurIntensity).toInt().coerceIn(1, 25)
val radius = (40 * blurIntensity).toInt().coerceIn(1, 40)
return blurBitmap(capturedImage, radius)
}
return capturedImage
@@ -1723,7 +1723,7 @@ class MainActivity : AppCompatActivity() {
val bgPixels = IntArray(w * h)
var blurredBg: android.graphics.Bitmap? = null
if (blurIntensity > 0f) {
val radius = (15 * blurIntensity).toInt().coerceIn(1, 25)
val radius = (25 * blurIntensity).toInt().coerceIn(1, 25)
blurredBg = blurBitmap(baseBg, radius)
blurredBg.getPixels(bgPixels, 0, w, 0, 0, w, h)
} else {
@@ -1778,7 +1778,7 @@ class MainActivity : AppCompatActivity() {
}
if (blurIntensity > 0f) {
val radius = (15 * blurIntensity).toInt().coerceIn(1, 15)
val radius = (25 * blurIntensity).toInt().coerceIn(1, 25)
return blurBitmap(capturedImage, radius)
}
return capturedImage
@@ -1835,7 +1835,7 @@ class MainActivity : AppCompatActivity() {
val bgPixels = IntArray(w * h)
var blurredBg: android.graphics.Bitmap? = null
if (blurIntensity > 0f) {
val radius = (25 * blurIntensity).toInt().coerceIn(1, 25)
val radius = (40 * blurIntensity).toInt().coerceIn(1, 40)
blurredBg = blurBitmap(baseBg, radius)
blurredBg.getPixels(bgPixels, 0, w, 0, 0, w, h)
} else {
@@ -1890,7 +1890,7 @@ class MainActivity : AppCompatActivity() {
}
if (blurIntensity > 0f) {
val radius = (25 * blurIntensity).toInt().coerceIn(1, 25)
val radius = (40 * blurIntensity).toInt().coerceIn(1, 40)
return blurBitmap(capturedImage, radius)
}
return capturedImage
@@ -1950,74 +1950,84 @@ class MainActivity : AppCompatActivity() {
}
private fun blurBitmap(src: android.graphics.Bitmap, radius: Int): android.graphics.Bitmap {
val scaleFactor = 4
val w = src.width
val h = src.height
val output = android.graphics.Bitmap.createBitmap(w, h, android.graphics.Bitmap.Config.ARGB_8888)
val downscaledW = (w / scaleFactor).coerceAtLeast(1)
val downscaledH = (h / scaleFactor).coerceAtLeast(1)
val downscaledBitmap = android.graphics.Bitmap.createScaledBitmap(src, downscaledW, downscaledH, true)
val pixels = IntArray(w * h)
src.getPixels(pixels, 0, w, 0, 0, w, h)
val r = (radius / scaleFactor).coerceAtLeast(1)
val temp = IntArray(w * h)
val r = radius.coerceAtLeast(1)
val windowSize = r * 2 + 1
val width = downscaledBitmap.width
val height = downscaledBitmap.height
val pixels = IntArray(width * height)
downscaledBitmap.getPixels(pixels, 0, width, 0, 0, width, height)
downscaledBitmap.recycle()
val blurredPixels = IntArray(width * height)
for (y in 0 until height) {
for (x in 0 until width) {
// Horizontal pass
for (y in 0 until h) {
val rowOffset = y * w
var rSum = 0
var gSum = 0
var bSum = 0
var count = 0
// Initialize window sum
for (dx in -r..r) {
val px = x + dx
if (px in 0 until width) {
val color = pixels[y * width + px]
rSum += android.graphics.Color.red(color)
gSum += android.graphics.Color.green(color)
bSum += android.graphics.Color.blue(color)
count++
val px = dx.coerceIn(0, w - 1)
val pixel = pixels[rowOffset + px]
rSum += (pixel shr 16) and 0xFF
gSum += (pixel shr 8) and 0xFF
bSum += pixel and 0xFF
}
}
val idx = y * width + x
blurredPixels[idx] = android.graphics.Color.rgb(rSum / count, gSum / count, bSum / count)
temp[rowOffset] = (0xFF shl 24) or ((rSum / windowSize) shl 16) or ((gSum / windowSize) shl 8) or (bSum / windowSize)
// Slide window
for (x in 1 until w) {
val oldPixelX = (x - 1 - r).coerceIn(0, w - 1)
val newPixelX = (x + r).coerceIn(0, w - 1)
val oldPixel = pixels[rowOffset + oldPixelX]
val newPixel = pixels[rowOffset + newPixelX]
rSum += ((newPixel shr 16) and 0xFF) - ((oldPixel shr 16) and 0xFF)
gSum += ((newPixel shr 8) and 0xFF) - ((oldPixel shr 8) and 0xFF)
bSum += (newPixel and 0xFF) - (oldPixel and 0xFF)
temp[rowOffset + x] = (0xFF shl 24) or ((rSum / windowSize) shl 16) or ((gSum / windowSize) shl 8) or (bSum / windowSize)
}
}
val finalPixels = IntArray(width * height)
for (x in 0 until width) {
for (y in 0 until height) {
// Vertical pass
for (x in 0 until w) {
var rSum = 0
var gSum = 0
var bSum = 0
var count = 0
// Initialize window sum
for (dy in -r..r) {
val py = y + dy
if (py in 0 until height) {
val color = blurredPixels[py * width + x]
rSum += android.graphics.Color.red(color)
gSum += android.graphics.Color.green(color)
bSum += android.graphics.Color.blue(color)
count++
val py = dy.coerceIn(0, h - 1)
val pixel = temp[py * w + x]
rSum += (pixel shr 16) and 0xFF
gSum += (pixel shr 8) and 0xFF
bSum += pixel and 0xFF
}
}
val idx = y * width + x
finalPixels[idx] = android.graphics.Color.rgb(rSum / count, gSum / count, bSum / count)
pixels[x] = (0xFF shl 24) or ((rSum / windowSize) shl 16) or ((gSum / windowSize) shl 8) or (bSum / windowSize)
// Slide window
for (y in 1 until h) {
val oldPixelY = (y - 1 - r).coerceIn(0, h - 1)
val newPixelY = (y + r).coerceIn(0, h - 1)
val oldPixel = temp[oldPixelY * w + x]
val newPixel = temp[newPixelY * w + x]
rSum += ((newPixel shr 16) and 0xFF) - ((oldPixel shr 16) and 0xFF)
gSum += ((newPixel shr 8) and 0xFF) - ((oldPixel shr 8) and 0xFF)
bSum += (newPixel and 0xFF) - (oldPixel and 0xFF)
pixels[y * w + x] = (0xFF shl 24) or ((rSum / windowSize) shl 16) or ((gSum / windowSize) shl 8) or (bSum / windowSize)
}
}
val tinyBlurred = android.graphics.Bitmap.createBitmap(width, height, android.graphics.Bitmap.Config.ARGB_8888)
tinyBlurred.setPixels(finalPixels, 0, width, 0, 0, width, height)
val upscaledDest = android.graphics.Bitmap.createScaledBitmap(tinyBlurred, w, h, true)
tinyBlurred.recycle()
return upscaledDest
output.setPixels(pixels, 0, w, 0, 0, w, h)
return output
}
override fun onDestroy() {