Question

我尝试从opencv跟进该教程，不同之处在于我使用的是Android。这是link。

在尝试获取新Mat的新值时，出现了错误。

newImageData[(y * mRgba.cols() + x) * mRgba.channels() + c] = saturate(alpha * pixelValue + beta);

这就是我使用的所有代码方法。

public Bitmap brightAndContrast(Bitmap bitmap){
    double alpha = 2.0;
    int beta = 50;

    Mat mRgba = new Mat();
    Mat mResult = Mat.zeros(mRgba.size(), mRgba.type());

    int width = bitmap.getWidth();
    int height = bitmap.getHeight();

    Bitmap resultBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Utils.bitmapToMat(bitmap, mRgba);

    byte[] imageData = new byte[(int) (mRgba.total()*mRgba.channels())];
    mRgba.get(0, 0, imageData);
    byte[] newImageData = new byte[(int) (mResult.total()*mResult.channels())];
    for (int y = 0; y < mRgba.rows(); y++) {
        for (int x = 0; x < mRgba.cols(); x++) {
            for (int c = 0; c < mRgba.channels(); c++) {
                double pixelValue = imageData[(y * mRgba.cols() + x) * mRgba.channels() + c];
                pixelValue = pixelValue < 0 ? pixelValue + 256 : pixelValue;
                newImageData[(y * mRgba.cols() + x) * mRgba.channels() + c] = saturate(alpha * pixelValue + beta); // this is where the line 101
            }
        }
    }
    mResult.put(0, 0, newImageData);


    Utils.matToBitmap(mResult, resultBitmap);

    return resultBitmap;
}
 private byte saturate(double val) {
    int iVal = (int) Math.round(val);
    iVal = iVal > 255 ? 255 : (iVal < 0 ? 0 : iVal);
    return (byte) iVal;
}

那么为什么它越界呢？这是我得到的错误

 java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
    at com.wannatry.tryapps.OpenCVConverter.brightAndContrast(OpenCVConverter.java:101)
    at com.wannatry.tryapps.MainActivity$15.onClick(MainActivity.java:232)
    at android.view.View.performClick(View.java:5740)
    at android.view.View$PerformClick.run(View.java:22947)

已编辑 这是教程中的C ++代码

new_image.at<Vec3b>(y,x)[c] = saturate_cast<uchar>( alpha*image.at<Vec3b>(y,x)[c] + beta );

并翻译为此代码

double pixelValue = imageData[(y * image.cols() + x) * image.channels() + c]; pixelValue = pixelValue < 0 ? pixelValue + 256 : pixelValue; newImageData[(y * image.cols() + x) * image.channels() + c] = saturate(alpha * pixelValue + beta);

如何解决索引超出范围？

0 个答案: