Jetpack Compose Coil2.0 高斯模糊

大家可以看Coil2.0.0的更新日志，在2.0中Coil的作者把BlurTransformation移除了。

在2.0想实现高斯模糊的话就把BlurTransformation复制过来到我们的项目中。

这里我们复制2.0之前最新的一个版本1.4.0的BlurTransformation

注意复制的时候不要把包名改成我们自己的包名，就用 coil.transform这个包名。

当然有很多地方报红，修改好后的代码：

package coil.transform

import android.content.Context
import android.graphics.Bitmap
import android.graphics.Paint
import android.renderscript.Allocation
import android.renderscript.Element
import android.renderscript.RenderScript
import android.renderscript.ScriptIntrinsicBlur
import androidx.core.graphics.applyCanvas
import androidx.core.graphics.createBitmap
import coil.size.Size

/**
 * A [Transformation] that applies a Gaussian blur to an image.
 *
 * @param context The [Context] used to create a [RenderScript] instance.
 * @param radius The radius of the blur.
 * @param sampling The sampling multiplier used to scale the image. Values > 1
 *  will downscale the image. Values between 0 and 1 will upscale the image.
 */

class BlurTransformation @JvmOverloads constructor(
    private val context: Context,
    private val radius: Float = DEFAULT_RADIUS,
    private val sampling: Float = DEFAULT_SAMPLING
) : Transformation {

    init {
        require(radius in 0.0..25.0) { "radius must be in [0, 25]." }
        require(sampling > 0) { "sampling must be > 0." }
    }

    override val cacheKey = "${BlurTransformation::class.java.name}-$radius-$sampling"

    override suspend fun transform(input: Bitmap, size: Size): Bitmap {
        val paint = Paint(Paint.ANTI_ALIAS_FLAG or Paint.FILTER_BITMAP_FLAG)

        val scaledWidth = (input.width / sampling).toInt()
        val scaledHeight = (input.height / sampling).toInt()
        val output = createBitmap(scaledWidth, scaledHeight, input.safeConfig)
        //val output = pool.get(scaledWidth, scaledHeight, input.safeConfig)
        output.applyCanvas {
            scale(1 / sampling, 1 / sampling)
            drawBitmap(input, 0f, 0f, paint)
        }

        var script: RenderScript? = null
        var tmpInt: Allocation? = null
        var tmpOut: Allocation? = null
        var blur: ScriptIntrinsicBlur? = null
        try {
            script = RenderScript.create(context)
            tmpInt = Allocation.createFromBitmap(script, output, Allocation.MipmapControl.MIPMAP_NONE, Allocation.USAGE_SCRIPT)
            tmpOut = Allocation.createTyped(script, tmpInt.type)
            blur = ScriptIntrinsicBlur.create(script, Element.U8_4(script))
            blur.setRadius(radius)
            blur.setInput(tmpInt)
            blur.forEach(tmpOut)
            tmpOut.copyTo(output)
        } finally {
            script?.destroy()
            tmpInt?.destroy()
            tmpOut?.destroy()
            blur?.destroy()
        }

        return output
    }

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        return other is BlurTransformation &&
                context == other.context &&
                radius == other.radius &&
                sampling == other.sampling
    }

    override fun hashCode(): Int {
        var result = context.hashCode()
        result = 31 * result + radius.hashCode()
        result = 31 * result + sampling.hashCode()
        return result
    }

    override fun toString(): String {
        return "BlurTransformation(context=$context, radius=$radius, sampling=$sampling)"
    }

    private companion object {
        private const val DEFAULT_RADIUS = 10f
        private const val DEFAULT_SAMPLING = 1f
    }


}

internal val Bitmap.safeConfig: Bitmap.Config
    get() = config ?: Bitmap.Config.ARGB_8888

最后是compose中Image的高斯模糊代码：

val painter = rememberAsyncImagePainter(
    model = ImageRequest.Builder(LocalContext.current)
        .data("https://example.com/image.jpg")
        .transformations(BlurTransformation(LocalContext.current))
        .build()
)
Image(painter = painter,
    contentDescription =null)

最后防止以后Coil的作者又把BlurTransformation重新加到新版本，导致编译出错，咱可以把BlurTransformation的名称改一下。