public void setMinWidth(float minWidth) {
        mMinWidth = convertDpToPx(minWidth);
        mLastWidth = (mMinWidth + mMaxWidth) / 2f;
    }
Set the minimum width of the stroke in pixel.

@param minWidth the width in dp.
signature-pad/src/main/java/com/github/gcacace/signaturepad/views/SignaturePad.java