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Zhirkevich Alexander Y
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Zhirkevich Alexander Y
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example/shared/src/androidMain/kotlin/BlurHashDecoder.android.kt
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| import android.graphics.Bitmap | ||
| import androidx.compose.ui.graphics.ImageBitmap | ||
| import androidx.compose.ui.graphics.asImageBitmap | ||
|
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| internal actual fun ImageBitmap.Companion.fromPixmap( | ||
| width: Int, | ||
| height: Int, | ||
| colors: IntArray | ||
| ) : ImageBitmap { | ||
| return Bitmap | ||
| .createBitmap(colors, width, height, Bitmap.Config.ARGB_8888) | ||
| .asImageBitmap() | ||
| } |
146 changes: 146 additions & 0 deletions
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example/shared/src/commonMain/kotlin/BlurHashDecoder.kt
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| import androidx.compose.ui.graphics.Color | ||
| import androidx.compose.ui.graphics.ImageBitmap | ||
| import androidx.compose.ui.graphics.toArgb | ||
| import kotlin.math.PI | ||
| import kotlin.math.cos | ||
| import kotlin.math.pow | ||
| import kotlin.math.withSign | ||
|
|
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| internal object BlurHashDecoder { | ||
|
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| fun decode( | ||
| blurHash: String, | ||
| width: Int, | ||
| height: Int, | ||
| punch: Float = 1f | ||
| ): ImageBitmap { | ||
| val numCompEnc = decode83(blurHash, 0, 1) | ||
| val numCompX = (numCompEnc % 9) + 1 | ||
| val numCompY = (numCompEnc / 9) + 1 | ||
| require(blurHash.length == 4 + 2 * numCompX * numCompY) { | ||
| "invalid hash" | ||
| } | ||
| val maxAcEnc = decode83(blurHash, 1, 2) | ||
| val maxAc = (maxAcEnc + 1) / 166f | ||
| val colors = Array(numCompX * numCompY) { i -> | ||
| if (i == 0) { | ||
| val colorEnc = decode83(blurHash, 2, 6) | ||
| decodeDc(colorEnc) | ||
| } else { | ||
| val from = 4 + i * 2 | ||
| val colorEnc = decode83(blurHash, from, from + 2) | ||
| decodeAc(colorEnc, maxAc * punch) | ||
| } | ||
| } | ||
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| return composeBitmap(width, height, numCompX, numCompY, colors) | ||
| } | ||
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| private fun decode83(str: String, from: Int = 0, to: Int = str.length): Int { | ||
| var result = 0 | ||
| for (i in from until to) { | ||
| val index = charMap[str[i]] ?: -1 | ||
| if (index != -1) { | ||
| result = result * 83 + index | ||
| } | ||
| } | ||
| return result | ||
| } | ||
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| private fun decodeDc(colorEnc: Int): FloatArray { | ||
| val r = colorEnc shr 16 | ||
| val g = (colorEnc shr 8) and 255 | ||
| val b = colorEnc and 255 | ||
| return floatArrayOf(srgbToLinear(r), srgbToLinear(g), srgbToLinear(b)) | ||
| } | ||
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| private fun srgbToLinear(colorEnc: Int): Float { | ||
| val v = colorEnc / 255f | ||
| return if (v <= 0.04045f) { | ||
| (v / 12.92f) | ||
| } else { | ||
| ((v + 0.055f) / 1.055f).pow(2.4f) | ||
| } | ||
| } | ||
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| private fun decodeAc(value: Int, maxAc: Float): FloatArray { | ||
| val r = value / (19 * 19) | ||
| val g = (value / 19) % 19 | ||
| val b = value % 19 | ||
| return floatArrayOf( | ||
| signedPow2((r - 9) / 9.0f) * maxAc, | ||
| signedPow2((g - 9) / 9.0f) * maxAc, | ||
| signedPow2((b - 9) / 9.0f) * maxAc | ||
| ) | ||
| } | ||
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| private fun signedPow2(value: Float) = value.pow(2f).withSign(value) | ||
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| private fun composeBitmap( | ||
| width: Int, height: Int, | ||
| numCompX: Int, numCompY: Int, | ||
| colors: Array<FloatArray> | ||
| ): ImageBitmap { | ||
| // use an array for better performance when writing pixel colors | ||
| val imageArray = IntArray(width * height) | ||
| val cosinesX = DoubleArray(width * numCompY) | ||
| val cosinesY = DoubleArray(height * numCompY) | ||
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| for (y in 0 until height) { | ||
| for (x in 0 until width) { | ||
| var r = 0f | ||
| var g = 0f | ||
| var b = 0f | ||
| for (j in 0 until numCompY) { | ||
| for (i in 0 until numCompX) { | ||
| val cosX = cosinesX.getCos(i, numCompX, x, width) | ||
| val cosY = cosinesY.getCos(j, numCompY, y, height) | ||
| val basis = (cosX * cosY).toFloat() | ||
| val color = colors[j * numCompX + i] | ||
| r += color[0] * basis | ||
| g += color[1] * basis | ||
| b += color[2] * basis | ||
| } | ||
| } | ||
| imageArray[x + width * y] = | ||
| Color(linearToSrgb(r), linearToSrgb(g), linearToSrgb(b)).toArgb() | ||
| } | ||
| } | ||
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| return ImageBitmap.fromPixmap(width, height, imageArray) | ||
| } | ||
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| private fun DoubleArray.getCos( | ||
| x: Int, | ||
| numComp: Int, | ||
| y: Int, | ||
| size: Int | ||
| ): Double { | ||
| return cos(PI * y * x / size).also { | ||
| this[x + numComp * y] = it | ||
| } | ||
| } | ||
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| private fun linearToSrgb(value: Float): Int { | ||
| val v = value.coerceIn(0f, 1f) | ||
| return if (v <= 0.0031308f) { | ||
| (v * 12.92f * 255f + 0.5f).toInt() | ||
| } else { | ||
| ((1.055f * v.pow(1 / 2.4f) - 0.055f) * 255 + 0.5f).toInt() | ||
| } | ||
| } | ||
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| private val charMap = listOf( | ||
| '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', | ||
| 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', | ||
| 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', | ||
| 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',', | ||
| '-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~' | ||
| ).mapIndexed { i, c -> c to i }.toMap() | ||
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| } | ||
|
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| internal expect fun ImageBitmap.Companion.fromPixmap( | ||
| width : Int, height : Int, colors : IntArray | ||
| ) : ImageBitmap |
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| @@ -0,0 +1,65 @@ | ||
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| import androidx.compose.runtime.Composable | ||
| import androidx.compose.runtime.remember | ||
| import androidx.compose.ui.geometry.Size | ||
| import androidx.compose.ui.graphics.ImageBitmap | ||
| import androidx.compose.ui.graphics.drawscope.DrawScope | ||
| import androidx.compose.ui.graphics.painter.Painter | ||
| import androidx.compose.ui.unit.IntSize | ||
| import kotlin.math.roundToInt | ||
| import kotlin.math.sqrt | ||
|
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| @Composable | ||
| public fun rememberBlurHashPainter( | ||
| hash : String, | ||
| width : Int = 0, | ||
| height : Int = 0, | ||
| quality : Float = 1f, | ||
| intensity : Float = 1f | ||
| ) : BlurHashPainter { | ||
| return remember(hash, width, height, quality, intensity) { | ||
| BlurHashPainter(hash, width, height, quality, intensity) | ||
| } | ||
| } | ||
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| /** | ||
| * @param hash blur hash of an image | ||
| * @param width image width. Used for intrinsic size only | ||
| * @param height image height. Used for intrinsic size only | ||
| * @param quality blur quality. Must be positive | ||
| * */ | ||
| public class BlurHashPainter( | ||
| public val hash : String, | ||
| width : Int = 0, | ||
| height : Int = 0, | ||
| private val quality : Float = 1f, | ||
| private val intensity : Float = 1f, | ||
| ) : Painter() { | ||
|
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| override val intrinsicSize: Size = Size( | ||
| width.takeIf { it > 0 }?.toFloat() ?: Float.NaN, | ||
| height.takeIf { it > 0 }?.toFloat() ?: Float.NaN, | ||
| ) | ||
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| private var cachedBitmap: ImageBitmap? = null | ||
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| override fun DrawScope.onDraw() { | ||
| val pixmapSize = (3000f * quality.coerceAtLeast(0f)) | ||
| .coerceAtLeast(100f) | ||
| val targetScale = sqrt(pixmapSize / (size.width * size.height)).coerceAtMost(1f) | ||
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| val targetWidth = (size.width * targetScale).roundToInt() | ||
| val targetHeight = (size.height * targetScale).roundToInt() | ||
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| val bitmap = cachedBitmap?.takeIf { | ||
| it.width >= targetWidth && it.width.toFloat() / it.height == targetWidth.toFloat() / targetHeight | ||
| } ?: BlurHashDecoder.decode(hash, targetWidth, targetHeight, intensity).also { | ||
| cachedBitmap = it | ||
| } | ||
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| drawImage( | ||
| image = bitmap, | ||
| dstSize = IntSize(size.width.roundToInt(), size.height.roundToInt()) | ||
| ) | ||
| } | ||
| } |
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20 changes: 20 additions & 0 deletions
20
example/shared/src/skikoMain/kotlin/BlurHashDecoder.skiko.kt
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,20 @@ | ||
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| import androidx.compose.ui.graphics.ImageBitmap | ||
| import androidx.compose.ui.graphics.ImageBitmapConfig | ||
| import androidx.compose.ui.graphics.asComposeImageBitmap | ||
| import androidx.compose.ui.graphics.asSkiaBitmap | ||
|
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| internal actual fun ImageBitmap.Companion.fromPixmap( | ||
| width: Int, | ||
| height: Int, | ||
| colors: IntArray | ||
| ) : ImageBitmap { | ||
|
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| val bgra = ByteArray(colors.size * 4) { | ||
| colors[it / 4].ushr((it % 4) * 8).toByte() | ||
| } | ||
|
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| return ImageBitmap(width, height, ImageBitmapConfig.Argb8888) | ||
| .asSkiaBitmap().apply { installPixels(bgra) } | ||
| .asComposeImageBitmap() | ||
| } |