Java中的图像处理

Question

I want to extract the pixel values of the jpeg image using the JAVA language, and need to store it in array(bufferdArray) for further manipulation. So how i can extract the pixel values from jpeg image format?

Answer 1

Have a look at BufferedImage.getRGB().

Here is a stripped-down instructional example of how to pull apart an image to do a conditional check/modify on the pixels. Add error/exception handling as necessary.

public static BufferedImage exampleForSO(BufferedImage image) {
BufferedImage imageIn = image;
BufferedImage imageOut = 
new BufferedImage(imageIn.getWidth(), imageIn.getHeight(), BufferedImage.TYPE_4BYTE_ABGR);
int width = imageIn.getWidth();
int height = imageIn.getHeight();
int[] imageInPixels = imageIn.getRGB(0, 0, width, height, null, 0, width);
int[] imageOutPixels = new int[imageInPixels.length];
for (int i = 0; i < imageInPixels.length; i++) {
    int inR = (imageInPixels[i] & 0x00FF0000) >> 16;
    int inG = (imageInPixels[i] & 0x0000FF00) >> 8;
    int inB = (imageInPixels[i] & 0x000000FF) >> 0;

    if (  conditionChecker_inRinGinB  ){
        // modify
    } else {
        // don't modify
    }

}
imageOut.setRGB(0, 0, width, height, imageOutPixels, 0, width);
return imageOut;
}

Answer 2

The easiest way to get a JPEG into a java-readable object is the following:

BufferedImage image = ImageIO.read(new File("MyJPEG.jpg"));

BufferedImage provides methods for getting RGB values at exact pixel locations in the image (XY integer coordinates), so it'd be up to you to figure out how you want to store that in a single-dimensional array, but that's the gist of it.

Answer 3

There is a way of taking a buffered image and converting it into an integer array, where each integer in the array represents the rgb value of a pixel in the image.

int[] pixels = ((DataBufferInt)image.getRaster().grtDataBuffer()).getData();

The interesting thing is, when an element in the integer array is edited, the corresponding pixel in the image is as well.

In order to find a pixel in the array from a set of x and y coordinates, you would use this method.

public void setPixel(int x, int y ,int rgb){
    pixels[y * image.getWidth() + x] = rgb;
}

Even with the multiplication and addition of coordinates, it is still faster than using the setRGB() method in the BufferedImage class.

EDIT: Also keep in mind, the image needs type needs to be that of TYPE_INT_RGB, and isn't by default. It can be converted by creating a new image of the same dimensions, and of the type of TYPE_INT_RGB. Then using the graphics object of the new image to draw the original image to the new one.

public BufferedImage toIntRGB(BufferedImage image){
    if(image.getType() == BufferedImage.TYPE_INT_RGB)
         return image;
    BufferedImage newImage = new BufferedImage(image.getWidth(), image.getHeight, BufferedImage.TYPE_INT_RGB);
    newImage.getGraphics().drawImage(image, 0, 0, null);
    return newImage;
}