我有一个代码,使用以下代码将具有灰色的位图转换为黑色和白色的位图：
// scan through all pixels
for (int x = 0; x < width; ++x) {
for (int y = 0; y < height; ++y) {
// get pixel color
pixel = bitmap.getPixel(x,y);
A = Color.alpha(pixel);
R = Color.red(pixel);
G = Color.green(pixel);
B = Color.blue(pixel);
int gray = (int) (0.2989 * R + 0.5870 * G + 0.1140 * B);
// use 128 as threshold,above -> white,below -> black
if (gray > 128)
gray = 255;
else
gray = 0;
// set new pixel color to output bitmap
bmOut.setPixel(x,y,Color.argb(A,gray,gray));
}
}
正如你所看到的那样,我遍历了原始位图的所有像素点,然后我将颜色的分量与给定的阈值进行比较,在这种情况下为128,然后如果它在上面我说它是白色,否则它将是一个黑色像素.
我现在想做的是一个可以改变该阈值的Spinner,然后BW图像会有所不同.
要做到这一点,我需要再次绘制所有图像,这是非常cpu的成本时间,它需要时间再次传输所有像素.
有没有办法实时使用不同的BW阈值更改图像？
有人告诉我使用GIF,然后我会做的只是改变GIF的查找表值,有人在Android上有这方面的知识吗？
解决方法
自问这个问题以来已经过了一点时间,但我碰到了这个寻找其他东西并碰巧得到了解决方案.
您可以在没有OpenCV或任何其他第三方库的情况下实现此目的,仅使用自API级别1以来的 ColorMatrixColorFilter.
您可以在没有OpenCV或任何其他第三方库的情况下实现此目的,仅使用自API级别1以来的 ColorMatrixColorFilter.
以下是您可以使用的矩阵：
//matrix that changes picture into gray scale
public static ColorMatrix createGreyMatrix() {
ColorMatrix matrix = new ColorMatrix(new float[] {
0.2989f,0.5870f,0.1140f,0.2989f,1,0
});
return matrix;
}
// matrix that changes gray scale picture into black and white at given threshold.
// It works this way:
// The matrix after multiplying returns negative values for colors darker than threshold
// and values bigger than 255 for the ones higher.
// Because the final result is always trimed to bounds (0..255) it will result in bitmap made of black and white pixels only
public static ColorMatrix createThresholdMatrix(int threshold) {
ColorMatrix matrix = new ColorMatrix(new float[] {
85.f,85.f,0.f,-255.f * threshold,0f,1f,0f
});
return matrix;
}
以下是如何使用它们：
BitmapFactory.Options options = new BitmapFactory.Options(); options.inScaled = false; //load source bitmap and prepare destination bitmap Bitmap pic = BitmapFactory.decodeResource(getResources(),R.drawable.thePicture,options); Bitmap result = Bitmap.createBitmap(pic.getWidth(),pic.getHeight(),Bitmap.Config.ARGB_8888); Canvas c = new Canvas(result); //first convert bitmap to grey scale: bitmapPaint.setColorFilter(new ColorMatrixColorFilter(createGreyMatrix())); c.drawBitmap(pic,bitmapPaint); //then convert the resulting bitmap to black and white using threshold matrix bitmapPaint.setColorFilter(new ColorMatrixColorFilter(createThresholdMatrix(128))); c.drawBitmap(result,bitmapPaint); //voilà! You can now draw the result bitmap anywhere You want: bitmapPaint.setColorFilter(null); otherCanvas.drawBitmap(result,null,new Rect(x,x + size,y + size),bitmapPaint);
希望这会对某人有所帮助.
