RenderScript错误地操作内核的输出

Question

我正在尝试使用Android的RenderScript在图像后面渲染一个半透明的圆圈,但是从RenderScript内核返回一个值时出了问题.

这是我的内核:

#pragma version(1)
#pragma rs java_package_name(be.abyx.aurora)
// We don't need very high precision floating points
#pragma rs_fp_relaxed

// Center position of the circle
int centerX = 0;
int centerY = 0;

// Radius of the circle
int radius = 0;

// Destination colour of the background can be set here.
float destinationR;
float destinationG;
float destinationB;
float destinationA;

static int square(int input) {
    return input * input;
}

uchar4 RS_KERNEL circleRender(uchar4 in, uint32_t x, uint32_t y) {
    //Convert input uchar4 to float4
    float4 f4 = rsUnpackColor8888(in);

    // Check if the current coordinates fall inside the circle
    if (square(x - centerX) + square(y - centerY) < square(radius)) {
        // Check if current position is transparent, we then need to add the background!)
        if (f4.a == 0) {
            uchar4 temp = rsPackColorTo8888(0.686f, 0.686f, 0.686f, 0.561f);
            return temp;
        }
    }

    return rsPackColorTo8888(f4);
}

现在,该rsPackColorTo8888()函数需要4个浮点数,其值介于0.0和1.0之间.然后通过计算每个浮点值的255倍来找到所得到的ARGB颜色.因此给定的浮点数对应于颜色R = 0.686*255 = 175,G = 0.686*255 = 175,B = 0.686*255 = 175且A = 0.561*255 = 143.

该rsPackColorTo8888()函数本身工作正常,但是当发现uchar4值从内核返回,一些真正怪异的发生.R,G和B值分别变为红色*α= 56,绿色*α= 56和蓝色*α= 56,其中Alpha为0.561.这意味着R,G和B的值不能大于A = 0.561*255.

手动设置输出而不是使用rsPackColorTo8888()产生完全相同的行为.我的意思是下面的代码产生完全相同的结果,这反过来证明这rsPackColorTo8888()不是问题:

if (square(x - centerX) + square(y - centerY) < square(radius)) {
    // Check if current position is transparent, we then need to add the background!)
    if (f4.a == 0) {
        uchar4 temp;
        temp[0] = 175;
        temp[1] = 175;
        temp[2] = 175;
        temp[3] = 143;
        return temp;
    }
}

这是调用脚本的Java代码:

@Override
public Bitmap renderParallel(Bitmap input, int backgroundColour, int padding) {
    ResizeUtility resizeUtility = new ResizeUtility();

    // We want to end up with a square Bitmap with some padding applied to it, so we use the
    // the length of the largest dimension (width or height) as the width of our square.
    int dimension = resizeUtility.getLargestDimension(input.getWidth(), input.getHeight()) + 2 * padding;

    Bitmap output = resizeUtility.createSquareBitmapWithPadding(input, padding);
    output.setHasAlpha(true);

    RenderScript rs = RenderScript.create(this.context);

    Allocation inputAlloc = Allocation.createFromBitmap(rs, output);
    Type t = inputAlloc.getType();

    Allocation outputAlloc = Allocation.createTyped(rs, t);

    ScriptC_circle_render circleRenderer = new ScriptC_circle_render(rs);

    circleRenderer.set_centerX(dimension / 2);
    circleRenderer.set_centerY(dimension / 2);
    circleRenderer.set_radius(dimension / 2);
    circleRenderer.set_destinationA(((float) Color.alpha(backgroundColour)) / 255.0f);
    circleRenderer.set_destinationR(((float) Color.red(backgroundColour)) / 255.0f);
    circleRenderer.set_destinationG(((float) Color.green(backgroundColour)) / 255.0f);
    circleRenderer.set_destinationB(((float) Color.blue(backgroundColour)) / 255.0f);

    circleRenderer.forEach_circleRender(inputAlloc, outputAlloc);
    outputAlloc.copyTo(output);

    inputAlloc.destroy();
    outputAlloc.destroy();
    circleRenderer.destroy();
    rs.destroy();

    return output;
}

当alpha设置为255(或1.0作为浮点数)时,返回的颜色值(在我的应用程序的Java代码中)是正确的.

我做错了什么,或者这真的是RenderScript实现中的某个错误？

注意:我已经在Oneplus 3T(Android 7.1.1),Nexus 5(Android 7.1.2),Android模拟器版本7.1.2和6.0上检查并验证了此行为

Answer 1

而不是使用类型传递值：

uchar4 temp = rsPackColorTo8888(0.686f, 0.686f, 0.686f, 0.561f);

尝试创建一个 float4 并传递它。

float4 newFloat4 = { 0.686, 0.686, 0.686, 0.561 };
uchar4 temp = rsPackColorTo8888(newFloat4);