Android Bitmap 模糊效果实现 (二)

本文首发地址 https://blog.csdn.net/CSqingchen/article/details/134656140
最新更新地址 https://gitee.com/chenjim/chenjimblog

通过 Android Bitmap 模糊效果实现 (一)，我们知道可以使用 Toolkit 实现 Bitmap 模糊，还能达到不错的效果。本文主要讲解另外几种实现Bitmap模糊的方法并对比效率。

使用 Vukan 模糊

Vulkan 是一种低开销、跨平台的 API，用于高性能 3D 图形。
Android平台包含 Khronos Group 的 Vulkan API规范的特定实现。
Android Vulkan 使用可以参考：
https://developer.android.com/ndk/guides/graphics/getting-started

使用 Vukan 模糊的核心代码如下，可参考 ImageProcessor.cpp

bool ImageProcessor::blur(float radius, int outputIndex) {RET_CHECK(1.0f <= radius && radius <= 25.0f);// Calculate gaussian kernel, this is equivalent to ComputeGaussianWeights at// https://cs.android.com/android/platform/superproject/+/master:frameworks/rs/cpu_ref/rsCpuIntrinsicBlur.cpp;l=57constexpr float e = 2.718281828459045f;constexpr float pi = 3.1415926535897932f;float sigma = 0.4f * radius + 0.6f;float coeff1 = 1.0f / (std::sqrtf(2.0f * pi) * sigma);float coeff2 = -1.0f / (2.0f * sigma * sigma);int32_t iRadius = static_cast<int>(std::ceilf(radius));float normalizeFactor = 0.0f;for (int r = -iRadius; r <= iRadius; r++) {const float value = coeff1 * std::powf(e, coeff2 * static_cast<float>(r * r));mBlurData.kernel[r + iRadius] = value;normalizeFactor += value;}normalizeFactor = 1.0f / normalizeFactor;for (int r = -iRadius; r <= iRadius; r++) {mBlurData.kernel[r + iRadius] *= normalizeFactor;}RET_CHECK(mBlurUniformBuffer->copyFrom(&mBlurData));// Apply a two-pass blur algorithm: a horizontal blur kernel followed by a vertical// blur kernel. This is equivalent to, but more efficient than applying a 2D blur// filter in a single pass. The two-pass blur algorithm has two kernels, each of// time complexity O(iRadius), while the single-pass algorithm has only one kernel,// but the time complexity is O(iRadius^2).auto cmd = mCommandBuffer->handle();RET_CHECK(beginOneTimeCommandBuffer(cmd));// The temp image is used as an output storage image in the first pass.mTempImage->recordLayoutTransitionBarrier(cmd, VK_IMAGE_LAYOUT_GENERAL, /*preserveData=*/false);// First pass: apply a horizontal gaussian blur.mBlurHorizontalPipeline->recordComputeCommands(cmd, &iRadius, *mInputImage, *mTempImage,mBlurUniformBuffer.get());// The temp image is used as an input sampled image in the second pass,// and the staging image is used as an output storage image.mTempImage->recordLayoutTransitionBarrier(cmd, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);mStagingOutputImage->recordLayoutTransitionBarrier(cmd, VK_IMAGE_LAYOUT_GENERAL,/*preserveData=*/false);// Second pass: apply a vertical gaussian blur.mBlurVerticalPipeline->recordComputeCommands(cmd, &iRadius, *mTempImage, *mStagingOutputImage,mBlurUniformBuffer.get());// Prepare for image copying from the staging image to the output image.mStagingOutputImage->recordLayoutTransitionBarrier(cmd, VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL);// Copy staging image to output image.recordImageCopyingCommand(cmd, *mStagingOutputImage, *mOutputImages[outputIndex]);// Submit to queue.RET_CHECK(endAndSubmitCommandBuffer(cmd, mContext->queue()));return true;
}

Vukan 环境、资源、Pipeline 相关代码如下

https://github.com/android/renderscript-samples/tree/main/RenderScriptMigrationSample/app/src/main/cpp

上层接口参见 VulkanImageProcessor

这里需要用到 libVkLayer_khronos_validation.so， 可以在以下地址下载新版本
https://github.com/KhronosGroup/Vulkan-ValidationLayers

使用 RenderEffect 模糊

实现代码如下

override fun blur(radius: Float, outputIndex: Int): Bitmap {params?.let {val blurRenderEffect = RenderEffect.createBlurEffect(radius, radius,Shader.TileMode.MIRROR)return applyEffect(it, blurRenderEffect, outputIndex)}throw RuntimeException("Not configured!")
}
private fun applyEffect(it: Params, renderEffect: RenderEffect, outputIndex: Int): Bitmap {it.renderNode.setRenderEffect(renderEffect)val renderCanvas = it.renderNode.beginRecording()renderCanvas.drawBitmap(it.bitmap, 0f, 0f, null)it.renderNode.endRecording()it.hardwareRenderer.createRenderRequest().setWaitForPresent(true).syncAndDraw()val image = it.imageReader.acquireNextImage() ?: throw RuntimeException("No Image")val hardwareBuffer = image.hardwareBuffer ?: throw RuntimeException("No HardwareBuffer")val bitmap = Bitmap.wrapHardwareBuffer(hardwareBuffer, null)?: throw RuntimeException("Create Bitmap Failed")hardwareBuffer.close()image.close()return bitmap
}
inner class Params(val bitmap: Bitmap, numberOfOutputImages: Int) {@SuppressLint("WrongConstant")val imageReader = ImageReader.newInstance(bitmap.width, bitmap.height,PixelFormat.RGBA_8888, numberOfOutputImages,HardwareBuffer.USAGE_GPU_SAMPLED_IMAGE or HardwareBuffer.USAGE_GPU_COLOR_OUTPUT)val renderNode = RenderNode("RenderEffect")val hardwareRenderer = HardwareRenderer()init {hardwareRenderer.setSurface(imageReader.surface)hardwareRenderer.setContentRoot(renderNode)renderNode.setPosition(0, 0, imageReader.width, imageReader.height)}
}

完整实例参考
RenderEffectImageProcessor.kt

使用 GLSL 模糊

主要流程：

• 将输入 Bitmap 转为纹理
  GLES31.glTexStorage2D( GLES31.GL_TEXTURE_2D, 1, GLES31.GL_RGBA8, mInputImage.width, mInputImage.height )
• 通过 OpenGL 处理纹理

完整实例参考 GLSLImageProcessor.kt

RS、Vukan、RenderEffect、GLSL 效率对比

通过示例 RenderScriptMigrationSample 可以看到
他们之间效率对比结果如下

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以上就是 Bitmap 模糊实现的方案二，希望对你有所帮助。
如果你在使用过程遇到问题，可以留言讨论。
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