如何写在Android中Renderscript卷积乘法？ [英] How to write a convolution multiplication in Android Renderscript?

问题描述

我是新来的Andr​​oid Renderscript。 我需要写一个卷积乘法RenderScript因为最终应用程序要在Android上运行。数据流将是一个图像。 更具体地讲，我不能够使用的forEach功能，虽然我可以用Java做写的核心逻辑，而且速度也太慢了！ 请帮忙！ 史蒂夫

I am new to Android Renderscript. I need to write a convolution multiplication in RenderScript since the final application is going to run on Android. Data stream is going to be an image. More specifically, I am not able to write the core logic using forEach functionality, though I can do it in Java, but speed it too slow! Please help! Steve

推荐答案

在rsForEach通话（或其他Renderscript功能），你可以通过绑定访问原始图像的相邻像素（或任何你正在使用的数据类型）原始图像分配到Renderscript内的指针在那里它可以被访问的一个数组。这是基于HelloCompute例如一个例子：

During the rsForEach call (or other Renderscript function), you can access the neighbouring pixels of the original image (or whatever type of data you are using) by binding the original image allocation to a pointer within the Renderscript where it can then be accessed as an array. Here is an example based upon the HelloCompute example:

#pragma version(1)
#pragma rs java_package_name(com.android.example.hellocompute)

rs_allocation gIn;
rs_allocation gOut;
rs_script gScript;

static int mImageWidth;
const uchar4 *gPixels;

const float4 kWhite = {
    1.0f, 1.0f, 1.0f, 1.0f
};
const float4 kBlack = {
    0.0f, 0.0f, 0.0f, 1.0f
};

void init() {
}

static const int kBlurWidth = 20;
static const float kMultiplier = 1.0f / (float)(kBlurWidth * 2 + 1);

void root(const uchar4 *v_in, uchar4 *v_out, const void *usrData, uint32_t x, uint32_t y) {
    float4 original = rsUnpackColor8888(*v_in);

    float4 colour = original * kMultiplier;

    int y_component = mImageWidth * y;

    for ( int i = -kBlurWidth; i < 0; i++) {
        float4 temp_colour;

        if ( (int)x + i >= 0) {
            temp_colour = rsUnpackColor8888(gPixels[x+i + y_component]);
        }
        else {
            temp_colour = kWhite;
        }

        colour += temp_colour * kMultiplier;
    }
    for ( int i = 1; i <= kBlurWidth; i++) {
        float4 temp_colour;

        if ( x + i < mImageWidth) {
            temp_colour = rsUnpackColor8888(gPixels[x+i + y_component]);
        }
        else {
            temp_colour = kWhite;
        }

        colour += temp_colour * kMultiplier;
    }

    colour.a = 1.0f;
    *v_out = rsPackColorTo8888(colour);
}


void filter() {
    mImageWidth = rsAllocationGetDimX(gIn);
    rsDebug("Image size is ", rsAllocationGetDimX(gIn), rsAllocationGetDimY(gOut));
    rsForEach(gScript, gIn, gOut, NULL);
}

从以下的Java调用。注意该呼叫到mScript.bind_gPixels（mInAllocation），该原始图像数据结合到gPixel指针在Renderscript，因此，使提供的图象数据作为数组

Called from the following Java. Note the call to mScript.bind_gPixels(mInAllocation) which binds the original image data to the gPixel pointer in the Renderscript and, therefore, makes the image data available as an array.

    mRS = RenderScript.create(this);

    mInAllocation = Allocation.createFromBitmap(mRS, mBitmapIn,
                                                Allocation.MipmapControl.MIPMAP_NONE,
                                                Allocation.USAGE_SCRIPT);
    mOutAllocation = Allocation.createTyped(mRS, mInAllocation.getType());

    mScript = new ScriptC_blur(mRS, getResources(), R.raw.blur);

    mScript.bind_gPixels(mInAllocation);

    mScript.set_gIn(mInAllocation);
    mScript.set_gOut(mOutAllocation);
    mScript.set_gScript(mScript);
    mScript.invoke_filter();
    mOutAllocation.copyTo(mBitmapOut);

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