Finding Java Image Pixels Information – ARGB (Alpha, Red, Green Blue)
Kushal Paudyal February 16th, 2012.This post has 2,532 views
In digital imaging, a pixel(or picture element) is the smallest item of information in an image. Pixels are normally arranged in a 2-dimensional grid, and are often represented using dots or squares. Each pixel is a sample of an original image, where more samples typically provide more-accurate representations of the original. The intensity of each pixel is variable; in color systems, each pixel has typically three or four components such as red, green, and blue, or cyan, magenta, yellow, and black.
The word pixel is based on a contraction of pix (“pictures”) and el (for “element”); similar formations with el for “element” include the words: voxel and texel. [Wikipedia]
In java 2D images, pixels are arranged in 2 dimensional array. If you take an image of dimension 200×300, there will be a total of 60,000 pixels. Each pixel is represented by a 32 bit integer. 32bit (4Bytes) represent 4 different color information. These color information, called ARGB, stand for Alpha, Red, Green and Blue. Each byte out of 4 Bytes of every pixel represents one of these color information.
In the following tutorial, you will learn
- How to read image from filesystem
- How to calculate the image height and width
- How to loop through each pixel and get pixel info
- Get alpha (transparency) value from the pixel
- Get Color info (red, green and blue) from the pixel
- How to do bit manipulation on an integer
package com.kushal.graphics;
/**
* @Author Kushal Paudyal
* www.sanjaal.com/java
* Last Modified On: 2009-10-21
*
* PrintImageARGBPixels.java
* Reads an image and prints out it's color and alpha
* information of individual pixels [Alpha, Red, Green Blue]
*/
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class PrintImageARGBPixels {
public static void main(String args[]) {
/**
* Read a sample image from the filesystem
*/
BufferedImage image = readImage("c:/temp/generalImage.jpg");
/**
* Call the method that prints out ARGB color Information.
* ARGB = Alpha, Red, Green and Blue
*/
printAllARGBDetails(image);
}
public static void printAllARGBDetails(BufferedImage image) {
int width = image.getWidth();
int height = image.getHeight();
System.out.println("Image Dimension: Height-" + height + ", Width-"
+ width);
System.out.println("Total Pixels: " + (height * width));
for (int i = 0; i < width; i++) {
for (int j = 0; j < height; j++) {
int pixel = image.getRGB(i, j);
System.out.println("Pixel Location(" + i + "," + j + ")- ["
+ getARGBPixelData(pixel) + "]");
}
}
}
/**
* Image Pixels are Arrays of Integers [32 bits/4Bytes]
* Consider a 32 pixel as 11111111-00110011-00111110-00011110
*
* First Byte From Left [11111111]= Alpha
* Second Byte From Left[00110011]= Red
* Third Byte From Left [00111110]= Green
* Fourth Byte From Left[00011110]= Blue
*
* The following method will do a proper bit shift and
* logical AND operation to extract the correct values
* of different color/alpha components.
*
*/
public static String getARGBPixelData(int pixel) {
String pixelARGBData = "";
/**
* Shift all pixels 24 bits to the right.
* Do a logical and with 0x000000FF
* i.e. 0000 0000 0000 0000 0000 0000 1111 1111
* You will get the alpha value for the pixel
*/
int alpha = (pixel >> 24) & 0x000000FF;
/**
* Shift all pixels 16 bits to the right.
* Do a logical and with 0x000000FF
* i.e. 0000 0000 0000 0000 0000 0000 1111 1111
* You will get the red value for the pixel
*/
int red = (pixel >> 16) & 0x000000FF;
/**
* Shift all pixels 8 bits to the right.
* Do a logical and with 0x000000FF
* i.e. 0000 0000 0000 0000 0000 0000 1111 1111
* You will get the green value for the pixel
*/
int green = (pixel >>8 ) & 0x000000FF;
/**
* Dont do any shift.
* Do a logical and with 0x000000FF
* i.e. 0000 0000 0000 0000 0000 0000 1111 1111
* You will get the blue value for the pixel
*/
int blue = (pixel) & 0x000000FF;
pixelARGBData = "Alpha: " + alpha + ", " + "Red: " + red + ", "
+ "Green: " + green + ", " + "Blue: " + blue;
return pixelARGBData;
}
/**
* This method reads an image from the file
* @param fileLocation -- > eg. "C:/testImage.jpg"
* @return BufferedImage of the file read
*/
public static BufferedImage readImage(String fileLocation) {
BufferedImage img = null;
try {
img = ImageIO.read(new File(fileLocation));
} catch (IOException e) {
e.printStackTrace();
}
return img;
}
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}
Sample Image Used In This Program (You can use any of your own).
Output of this program on a sample Image:
Note that I have shortened the output by removing many lines from in between. This is because I took a 122×122 image and there were a total of 14884 pixel info printed on the screen.
The complete output file is available here.
Image Dimension: Height-122, Width-122 Total Pixels: 14884 Pixel Location(0,0)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,1)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,2)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,3)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,4)- [Alpha: 255, Red: 255, Green: 254, Blue: 255] Pixel Location(0,5)- [Alpha: 255, Red: 255, Green: 254, Blue: 255] Pixel Location(0,6)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,7)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,8)- [Alpha: 255, Red: 254, Green: 255, Blue: 255] Pixel Location(0,9)- [Alpha: 255, Red: 254, Green: 255, Blue: 255] Pixel Location(0,10)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,11)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,12)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,13)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,14)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,15)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(0,16)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] . . . Pixel Location(90,26)- [Alpha: 255, Red: 216, Green: 217, Blue: 219] Pixel Location(90,27)- [Alpha: 255, Red: 219, Green: 215, Blue: 216] Pixel Location(90,28)- [Alpha: 255, Red: 216, Green: 216, Blue: 216] Pixel Location(90,29)- [Alpha: 255, Red: 210, Green: 214, Blue: 213] Pixel Location(90,30)- [Alpha: 255, Red: 206, Green: 210, Blue: 209] Pixel Location(90,31)- [Alpha: 255, Red: 219, Green: 212, Blue: 202] Pixel Location(90,32)- [Alpha: 255, Red: 235, Green: 205, Blue: 179] Pixel Location(90,33)- [Alpha: 255, Red: 221, Green: 167, Blue: 121] Pixel Location(90,34)- [Alpha: 255, Red: 213, Green: 132, Blue: 66] Pixel Location(90,35)- [Alpha: 255, Red: 220, Green: 130, Blue: 52] Pixel Location(90,36)- [Alpha: 255, Red: 212, Green: 133, Blue: 56] Pixel Location(90,37)- [Alpha: 255, Red: 196, Green: 139, Blue: 72] Pixel Location(90,38)- [Alpha: 255, Red: 185, Green: 161, Blue: 115] Pixel Location(90,39)- [Alpha: 255, Red: 206, Green: 203, Blue: 160] Pixel Location(90,40)- [Alpha: 255, Red: 207, Green: 213, Blue: 153] Pixel Location(90,41)- [Alpha: 255, Red: 174, Green: 189, Blue: 120] Pixel Location(90,42)- [Alpha: 255, Red: 160, Green: 183, Blue: 113] Pixel Location(90,43)- [Alpha: 255, Red: 124, Green: 155, Blue: 114] . . . Pixel Location(121,105)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,106)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,107)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,108)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,109)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,110)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,111)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,112)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,113)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,114)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,115)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,116)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,117)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,118)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,119)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,120)- [Alpha: 255, Red: 255, Green: 255, Blue: 255] Pixel Location(121,121)- [Alpha: 255, Red: 255, Green: 255, Blue: 255]
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Originally posted 2009-10-22 08:31:56.
- JAVA - Graphics 2D
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