Java image library to deskew and crop images

Question

Does anybody have a suggestion for a java library that performs automatic cropping and deskewing of images (like those retrieved from a flatbed scanner)?

Answer 1

Deskewing

Take a look at Tess4j (Java JNA wrapper for Tesseract).

You can combine ImageDeskew.getSkewAngle() with ImageHelper.rotate(BufferedImage image, double angle).

There is an example on how to use it on the test folder of the tess4j project Tesseract1Test.java

public void testDoOCR_SkewedImage() throws Exception {
    logger.info("doOCR on a skewed PNG image");
    File imageFile = new File(this.testResourcesDataPath, "eurotext_deskew.png");
    BufferedImage bi = ImageIO.read(imageFile);
    ImageDeskew id = new ImageDeskew(bi);
    double imageSkewAngle = id.getSkewAngle(); // determine skew angle
    if ((imageSkewAngle > MINIMUM_DESKEW_THRESHOLD || imageSkewAngle < -(MINIMUM_DESKEW_THRESHOLD))) {
        bi = ImageHelper.rotateImage(bi, -imageSkewAngle); // deskew image
    }

    String expResult = "The (quick) [brown] {fox} jumps!\nOver the $43,456.78  #90 dog";
    String result = instance.doOCR(bi);
    logger.info(result);
    assertEquals(expResult, result.substring(0, expResult.length()));
}