如果要让rsForEach函数调用每个图像行的root(),必须在一个Allocation中传递一个大小与行数相同的长度,然后计算出应该在哪个行上运行root()(类似于在每列上操作).然后,RenderScript应该将工作分配到可用资源上运行(在多核设备上同时处理多行).

您可以通过传递给予图像行中的偏移(在图像数据数组中)的分配来实现. root()中的v_in参数就是行偏移量.由于rsForEach调用正在运行的分配不是映像数据,您无法使用v_out参数写入映像,并且必须单独绑定输出映像.

这里有一些RenderScript显示：

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

rs_allocation gIn;
rs_allocation gOut;
rs_script gScript;

int mImageWidth;
const uchar4 *gInPixels;
uchar4 *gOutPixels;

void init() {
}

static const int kBlurWidth = 20;

//
// This is called per row.
// The row indices are passed in as v_in or you could also use the x argument and multiply it by image width.
//
void root(const int32_t *v_in,int32_t *v_out,const void *usrData,uint32_t x,uint32_t y) {
    float3 blur[kBlurWidth];
    float3 cur_colour = {0.0f,0.0f,0.0f};

    for ( int i = 0; i < kBlurWidth; i++) {
        float3 init_colour = {0.0f,0.0f};
        blur[i] = init_colour;
    }

    int32_t row_index = *v_in;
    int blur_index = 0;

    for ( int i = 0; i < mImageWidth; i++) {
        float4 pixel_colour = rsUnpackColor8888(gInPixels[i + row_index]);

        cur_colour -= blur[blur_index];
        blur[blur_index] = pixel_colour.rgb;
        cur_colour += blur[blur_index];

        blur_index += 1;
        if ( blur_index >= kBlurWidth) {
            blur_index = 0;
        }

        gOutPixels[i + row_index] = rsPackColorTo8888(cur_colour/(float)kBlurWidth);
        //gOutPixels[i + row_index] = rsPackColorTo8888(pixel_colour);
    }
}


void filter() {
    rsDebug("Number of rows:",rsAllocationGetDimX(gIn));
    rsForEach(gScript,gIn,gOut,NULL);
}

这将使用以下Java进行设置：

mBlurRowScript = new ScriptC_blur_row(mRS,getResources(),R.raw.blur_row);

    int row_width = mBitmapIn.getWidth();

    //
    // Create an allocation that indexes each row.
    //
    int num_rows = mBitmapIn.getHeight();
    int[] row_indices = new int[num_rows];
    for ( int i = 0; i < num_rows; i++) {
        row_indices[i] = i * row_width;
    }
    Allocation row_indices_alloc = Allocation.createSized( mRS,Element.I32(mRS),num_rows,Allocation.USAGE_SCRIPT);
    row_indices_alloc.copyFrom(row_indices);

    //
    // The image data has to be bound to the pointers within the RenderScript so it can be accessed
    // from the root() function.
    //
    mBlurRowScript.bind_gInPixels(mInAllocation);
    mBlurRowScript.bind_gOutPixels(mOutAllocation);

    // Pass in the image width
    mBlurRowScript.set_mImageWidth(row_width);

    //
    // Pass in the row indices Allocation as the input. It is also passed in as the output though the output is not used.
    //
    mBlurRowScript.set_gIn(row_indices_alloc);
    mBlurRowScript.set_gOut(row_indices_alloc);
    mBlurRowScript.set_gScript(mBlurRowScript);
    mBlurRowScript.invoke_filter();