检测图像中黑色像素

问题描述：

我如何从canvas.drawcircle ..

how i can detect black pixel from a circle drawn by canvas.drawcircle..

canvas.drawCircle((float)(myMidPoint.x - myEyesDistance/2.0), myMidPoint.y, (float)30.0, myPaint);

int x1=(int) (myMidPoint.x) /2;

int y1=(int)(myMidPoint.y)/2;
// int x2=(int) (myMidPoint.x + myEyesDistance/2.0);
// int y2=(int) myMidPoint.y;
int pixelColor = myBitmap.getPixel(x1,y1);
if(pixelColor == Color.BLACK) {
    //The pixel is black
    System.out.println("pixel black");
} else {
    //The pixel was white
    System.out.println("pixel white");
}

我也问过眼前的问题，但没有更新。谁能帮我来说这是非常紧迫的。希望你们能帮助我。 Plzz看到link

答

Color.BLACK是重新ARGB十六进制值0xff000000的presentation整数。所以，你的说法是检查在圆圈的中心点是完全一样的透明度，红色值，蓝色值和绿色值Color.BLACK。

Color.BLACK is the integer representation of argb Hex value 0xff000000. So your statement is checking whether a center point in the circle is exactly the same transparency, red value, blue value and green value as Color.BLACK.

有几个选项：

您可以尝试使用只是比较RGB值

You can try comparing just the rgb value by using

if(Color.rgb(Color.red(Color.BLACK), Color.green(Color.BLACK), Color.blue(Color.BLACK) == Color.rgb(Color.red(pixelColor), Color.green(pixelColor), Color.blue(pixelColor))

另外，你可以扫描一个黑色（0x000000处）像素的整个圆。

Alternatively you could scan the entire circle for a black (0x000000) pixel.

另外，您可以使用色差算法，并可以为你所需要的测试不同的公差。这可能会帮助您如何比较两种颜色的。

Alternatively you could use a Color difference algorithm and you can test different tolerances for what you need. This may help you How to compare two colors.

以下尚未经过测试，但会给你一个想法，哪个方向的，你也可以考虑：

The following hasn't been tested, but will give you an idea of which direction you could take also:

//mid points x1 and y1
int x1=(int) (myMidPoint.x) /2;
int y1=(int)(myMidPoint.y)/2;
int radius = 30;
int topPoint = y1 - radius;
int leftPoint = x1 - radius;
int rightPoint = x1 + radius;
int bottomPoint = y1 + radius;
int scanWidth = 0;
for(int i = topPoint; i < bottomPoint; i++) 
{

    if(i <= y1)
    {
        scanWidth++;
    }
    else {
        scanWidth--;
    }
    for(int j = x1 - scanWidth; j < x1 + scanWidth; j++)
    {
        int pixelColor = myBitmap.getPixel(j,i);
        if(Color.rgb(Color.red(Color.BLACK), Color.green(Color.BLACK), Color.blue(Color.BLACK) == Color.rgb(Color.red(pixelColor), Color.green(pixelColor), Color.blue(pixelColor))
        {
            System.out.println("pixel black");
        }
    } 
}

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