识别图片内容报错：
14:42:17.089 [main] ERROR net.sourceforge.tess4j.Tesseract – Error reading PNG metadata
javax.imageio.IIOException: Error reading PNG metadata
at com.sun.imageio.plugins.png.PNGImageReader.readMetadata(PNGImageReader.java:796)
at com.sun.imageio.plugins.png.PNGImageReader.readImage(PNGImageReader.java:1256)
at com.sun.imageio.plugins.png.PNGImageReader.read(PNGImageReader.java:1614)
at javax.imageio.ImageReader.readAll(ImageReader.java:1066)
at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:226)
at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:194)
at tools.image.ImageUtil.getString(ImageUtil.java:31)
at tools.image.ImageUtil.main(ImageUtil.java:40)
Caused by: javax.imageio.IIOException: Failed to read a chunk of type 1933723988
at com.sun.imageio.plugins.png.PNGImageReader.readMetadata(PNGImageReader.java:790)
… 7 common frames omitted
javax.imageio.IIOException: Error reading PNG metadata
下面左边是刚开始使用的图片，图片是自己裁剪过的，识别的时候报了上面的错，查看图片发现图片上的字很模糊，怀疑是这个导致的报错，后来把图片转换为灰度图像，再识别就可以了
