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Java Convolution

Hi I am in need of some help. I need to write a convolution method from scratch that takes in the following inputs: int[][] and BufferedImage inputImage. I can assume that the kernel has size 3x3.
My approach is to do the follow:
convolve inner pixels
convolve corner pixels
convolve outer pixels
In the program that I will post below I believe I convolve the inner pixels but I am a bit lost at how to convolve the corner and outer pixels. I am aware that corner pixels are at (0,0), (width-1,0), (0, height-1) and (width-1,height-1). I think I know to how approach the problem but not sure how to execute that in writing though. Please to aware that I am very new to programming :/ Any assistance will be very helpful to me.
import java.awt.*;
import java.awt.image.BufferedImage;
import com.programwithjava.basic.DrawingKit;
import java.util.Scanner;
public class Problem28 {
// maximum value of a sample
private static final int MAX_VALUE = 255;
//minimum value of a sample
private static final int MIN_VALUE = 0;
public BufferedImage convolve(int[][] kernel, BufferedImage inputImage) {
}
public BufferedImage convolveInner(double center, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage1 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 1; x < width - 1; x++) {
for (int y = 1; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) center*red;
int innergreen = (int) center*green;
int innerblue = (int) center*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage1.setRGB(x, y, newRgbvalue);
}
}
return inputImage1;
}
public BufferedImage convolveEdge(double edge, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage2 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 0; x < width - 1; x++) {
for (int y = 0; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) edge*red;
int innergreen = (int) edge*green;
int innerblue = (int) edge*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage2.setRGB(x, y, newRgbvalue);
}
}
return inputImage2;
}
public BufferedImage convolveCorner(double corner, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage3 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 0; x < width - 1; x++) {
for (int y = 0; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) corner*red;
int innergreen = (int) corner*green;
int innerblue = (int) corner*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage3.setRGB(x, y, newRgbvalue);
}
}
return inputImage3;
}
public static void main(String[] args) {
DrawingKit dk = new DrawingKit("Compositor", 1000, 1000);
BufferedImage p1 = dk.loadPicture("image/pattern1.jpg");
Problem28 c = new Problem28();
BufferedImage p5 = c.convolve();
dk.drawPicture(p5, 0, 100);
}
}
I changed the code a bit but the output comes out as black. What did I do wrong:
import java.awt.*;
import java.awt.image.BufferedImage;
import com.programwithjava.basic.DrawingKit;
import java.util.Scanner;
public class Problem28 {
// maximum value of a sample
private static final int MAX_VALUE = 255;
//minimum value of a sample
private static final int MIN_VALUE = 0;
public BufferedImage convolve(int[][] kernel, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage1 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//for every pixel
for (int x = 0; x < width; x ++) {
for (int y = 0; y < height; y ++) {
int colorValue = inputImage.getRGB(x,y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed();
int green = pixelColor.getGreen();
int blue = pixelColor.getBlue();
double gray = 0;
//multiply every value of kernel with corresponding image pixel
for (int i = 0; i < 3; i ++) {
for (int j = 0; j < 3; j ++) {
int imageX = (x - 3/2 + i + width) % width;
int imageY = (x -3/2 + j + height) % height;
int RGB = inputImage.getRGB(imageX, imageY);
int GRAY = (RGB) & 0xff;
gray += (GRAY*kernel[i][j]);
}
}
int out;
out = (int) Math.min(Math.max(gray * 1, 0), 255);
inputImage1.setRGB(x, y, new Color(out,out,out).getRGB());
}
}
return inputImage1;
}
public static void main(String[] args) {
int[][] newArray = {{1/9, 1/9, 1/9}, {1/9, 1/9, 1/9}, {1/9, 1/9, 1/9}};
DrawingKit dk = new DrawingKit("Problem28", 1000, 1000);
BufferedImage p1 = dk.loadPicture("image/pattern1.jpg");
Problem28 c = new Problem28();
BufferedImage p2 = c.convolve(newArray, p1);
dk.drawPicture(p2, 0, 100);
}
}

Welcome ewuzz! I wrote a convolution using CUDA about a week ago, and the majority of my experience is with Java, so I feel qualified to provide advice for this problem.
Rather than writing all of the code for you, the best way to solve this large program is to discuss individual elements. You mentioned you are very new to programming. As the programs you write become more complex, it's essential to write small working snippets before combining them into a large successful program (or iteratively add snippets). With this being said, it's already apparent you're trying to debug a ~100 line program, and this approach will cost you time in most cases.
The first point to discuss is the general approach you mentioned. If you think about the program, what is the simplest and most repeated step? Obviously this is the kernel/mask step, so we can start from here. When you convolute each pixel, you are performing a similar option, regardless of the position (corner, edge, inside). While there are special steps necessary for these edge cases, they share similar underlying steps. If you try to write code for each of these cases separately, you will have to update the code in multiple (three) places with each adjustment and it will make the whole program more difficult to grasp.
To support my point above, here's what happened when I pasted your code into IntelliJ. This illustrates the (yellow) red flag of using the same code in multiple places:
The concrete way to fix this problem is to combine the three convolve methods into a single one and use if statements for edge-cases as necessary.
Our pseudocode with this change:
convolve(kernel, inputImage)
for each pixel in the image
convolve the single pixel and check edge cases
endfor
end
That seems pretty basic right? If we are able to successfully check edge cases, then this extremely simple logic will work. The reason I left it so general above to show how convolve the single pixel and check edge cases is logically grouped. This means it's a good candidate for extracting a method, which could look like:
private void convolvePixel(int x, int y, int[][] kernel, BufferedImage input, BufferedImage output)
Now to implement our method above, we will need to break it into a few steps, which we may then break into more steps if necessary. We'll need to look at the input image, if possible for each pixel accumulate the values using the kernel, and then set this in the output image. For brevity I will only write pseudocode from here.
convolvePixel(x, y, kernel, input, output)
accumulation = 0
for each row of kernel applicable pixels
for each column of kernel applicable pixels
if this neighboring pixel location is within the image boundaries then
input color = get the color at this neighboring pixel
adjusted value = input color * relative kernel mask value
accumulation += adjusted value
else
//handle this somehow, mentioned below
endif
endfor
endfor
set output pixel as accumulation, assuming this convolution method does not require normalization
end
The pseudocode above is already relatively long. When implementing you could write methods for the if and the else cases, but it you should be fine with this structure.
There are a few ways to handle the edge case of the else above. Your assignment probably specifies a requirement, but the fancy way is to tile around, and pretend like there's another instance of the same image next to this input image. Wikipedia explains three possibilities:
Extend - The nearest border pixels are conceptually extended as far as necessary to provide values for the convolution. Corner pixels are extended in 90° wedges. Other edge pixels are extended in lines.
Wrap - (The method I mentioned) The image is conceptually wrapped (or tiled) and values are taken from the opposite edge or corner.
Crop - Any pixel in the output image which would require values from beyond the edge is skipped. This method can result in the output image being slightly smaller, with the edges having been cropped.
A huge part of becoming a successful programmer is researching on your own. If you read about these methods, work through them on paper, run your convolvePixel method on single pixels, and compare the output to your results by hand, you will find success.
Summary:
Start by cleaning-up your code before anything.
Group the same code into one place.
Hammer out a small chunk (convolving a single pixel). Print out the result and the input values and verify they are correct.
Draw out edge/corner cases.
Read about ways to solve edge cases and decide what fits your needs.
Try implementing the else case through the same form of testing.
Call your convolveImage method with the loop, using the convolvePixel method you know works. Done!
You can look up pseudocode and even specific code to solve the exact problem, so I focused on providing general insight and strategies I have developed through my degree and personal experience. Good luck and please let me know if you want to discuss anything else in the comments below.
Java code for multiple blurs via convolution.

Java- How to remove background color from an image

First off I am new to this and also coding. I apologize in advance for anything that is misleading.
I am currently writing a Java program that uses an image as input. What I have currently is scanning each pixel by the width and height of the image saving the HSB in an array and then outputting the percentage of each color in the image. I now want to omit the background from that calculation. To start off lets just say the background is white. There are also pixels in the image that are not in the background that is white though.
thank you,

Oh, it's not as simple as you hope.
You cannot simply detect what's a background and what is part of image pixel by pixel.
You might try looking at this post to see how to remove one color layer of the image.
But detecting if the white pixel is a part of background or already the image?!
There are multiple possible ways:
assuming that background is just around and when (looking from any
side to the center) color changes, that is the end of the
"background". You can check every row and column from side to center
and keep record of where the "background" color ends.
or similar approach - if at least at one (of four) direction looking from the pixel to the side there is no color changes (it goes white all the way to the side), than it is part of background.
Or just take a look at another
post. From this you can try working your way up.
Anyway - you have to create a logic of detecting which (i.e.) white pixels are part of the picture and which are part of background.
I hope this at least gives you a bit more knowledge.

I am not sure what you mean. There is no code, so I can only give you an example. From what I have understood, you want to skip doing a calculation when the color is the same as the background. That is very simple. You can do something like this:
for(int x = 0; x < width; x++) {
for(int y = 0; y < height; y++) {
Color pixelColor = get pixel color at x and y;
Color backgroundColor = the background color;
if(pixelColor != backgroundColor) {
//Calculation will be done here
}
}
}
If this does not help you or you have any other questions, ask me.

Here is an example of full working code.
You can add a cursor to pick color and jslider for fuzz or threshold. Use backColor and threshold for your needs.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class Convert {
private static final Color backColor = new Color(255,255,255);
private static final int THRESHOLD = 35;
private static final int TRANSPARENT = 0; // 0x00000000;
static File base = new File("f://mortar1.png");
static File base2 = new File("f://outtrans.png");
public static void main(String[] args) throws IOException {
System.out.println("Convert.main()");
for (File file : base.listFiles())
{
BufferedImage initImage = ImageIO.read(base);
int width = initImage.getWidth(null),
height = initImage.getHeight(null);
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics g = image.getGraphics();
g.drawImage(initImage, 0, 0, null);
System.out.println("before: " + image.getRGB(0, 0));
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
int pixel = image.getRGB(x, y);
Color color = new Color(pixel);
int dr = Math.abs(color.getRed() - backColor.getRed()),
dg = Math.abs(color.getGreen() - backColor.getGreen()),
db = Math.abs(color.getBlue() - backColor.getBlue());
if (dr < THRESHOLD && dg < THRESHOLD && db < THRESHOLD) {
image.setRGB(x, y, TRANSPARENT);
}
}
}
System.out.println(" after: " + image.getRGB(0, 0));
File file = new File("f://outtrans1.png");
ImageIO.write(image, "png", file);
}
}
}

Or simple set a png file with empty fill..
This idea seems good for me. But if you don't agree, please, tell me causes)

How to change the brightness of an Image

My Question: I want to be able to change the brightness of a resource image and have three instances of it as ImageIcons. One at 50% brightness (so darker), another at 75% brightness (a little brighter), and finally another at 100% brightness (the same as the original image). I also want to preserve transparency.
What I've tried: I've searched around and it looks like the best solution is using RescaleOp, but I just can't figure it out. I don't know what the scaleFactor and the offset is all about. Here's my code for what I've tried.
public void initialize(String imageLocation, float regularBrightness, float focusedBrightness, float pressedBrightness, String borderTitle) throws IOException {
BufferedImage bufferedImage = ImageIO.read(ButtonIcon.class.getResource(imageLocation));
setRegularIcon(getAlteredImageIcon(bufferedImage, regularBrightness));
setFocusedIcon(getAlteredImageIcon(bufferedImage, focusedBrightness));
setPressedIcon(getAlteredImageIcon(bufferedImage, pressedBrightness));
setTitle(borderTitle);
init();
}
private ImageIcon getAlteredImageIcon(BufferedImage bufferedImage, float brightness) {
RescaleOp rescaleOp = new RescaleOp(brightness, 0, null);
return new ImageIcon(rescaleOp.filter(bufferedImage, null));
}
The call would be something like this:
seeATemplateButton.initialize("/resources/templateIcon-regular.png", 100f, 75f, 50f, "See A Template");
//I think my 100f, 75f, 50f variables need to change, but whenever I change them it behaves unexpectedly (changes colors and stuff).
What happens with that code: The image appears "invisible" I know it's there because it's on a JLabel with a mouse clicked event on it and that works just fine. If I just skip the brightness changing part and say setRegularIcon(new ImageIcon(Button.class.getResource(imageLocation)); it works just fine, but obviously it's not any darker.
What I think I need: Some help understanding what offset, scaleFactor, and the filter method mean/do, and consequently what numbers to give for the brightness variable.
Any help would be greatly appreciated! Thanks!

The doc says:
The pseudo code for the rescaling operation is as follows:
for each pixel from Source object {
for each band/component of the pixel {
dstElement = (srcElement*scaleFactor) + offset
}
}
It's just a linear transformation on every pixel. The parameters for that transformation are scaleFactor and offset. If you want 100% brightness, this transform must be an identity, i.e. dstElement = srcElement. Setting scaleFactor = 1 and offset = 0 does the trick.
Now suppose you want to make the image darker, at 75% brightness like you say. That amounts to multiplying the pixel values by 0.75. You want: dstElement = 0.75 * srcElement. So setting scaleFactor = 0.75 and offset = 0 should do the trick. The problem with your values is that they go from 0 to 100, you need to use values between 0 and 1.

I would suggest just writing over the image with a semi-transparent black.
Assuming you want to write directly on the image:
Graphics g = img.getGraphics();
float percentage = .5f; // 50% bright - change this (or set dynamically) as you feel fit
int brightness = (int)(256 - 256 * percentage);
g.setColor(new Color(0,0,0,brightness));
g.fillRect(0, 0, img.getWidth(), img.getHeight());
Or if you're just using the image for display purposes, do it in the paintComponent method. Here's an SSCCE:
import java.awt.*;
import java.awt.image.*;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
public class ImageBrightener extends JPanel{
BufferedImage img;
float percentage = 0.5f;
public Dimension getPreferredSize(){
return new Dimension(img.getWidth(), img.getHeight());
}
public ImageBrightener(){
try {
img = ImageIO.read(new URL("http://media.giantbomb.com/uploads/0/1176/230441-thehoff_super.jpeg"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g.drawImage(img, 0, 0, this);
int brightness = (int)(256 - 256 * percentage);
g.setColor(new Color(0,0,0,brightness));
g.fillRect(0, 0, getWidth(), getHeight());
}
public static void main(String[] args){
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new ImageBrightener());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
EDIT
Assuming the same code as above, you can manipulate everything besides the Alpha by messing with the rasterizer. Here's an example (paint shadedImage instead of img if using this exmaple). Please note this doesn't catch edge cases of RGB values greater than 256 and less than 0.
img = ImageIO.read(new URL("http://media.giantbomb.com/uploads/0/1176/230441-thehoff_super.jpeg"));
shadedImage = new BufferedImage(img.getWidth(), img.getWidth(), BufferedImage.TYPE_INT_ARGB);
shadedImage.getGraphics().drawImage(img, 0, 0, this);
WritableRaster wr = shadedImage.getRaster();
int[] pixel = new int[4];
for(int i = 0; i < wr.getWidth(); i++){
for(int j = 0; j < wr.getHeight(); j++){
wr.getPixel(i, j, pixel);
pixel[0] = (int) (pixel[0] * percentage);
pixel[1] = (int) (pixel[1] * percentage);
pixel[2] = (int) (pixel[2] * percentage);
wr.setPixel(i, j, pixel);
}
}

A few more examples for study:
AlphaTest rescales just the alpha transparency of an image between zero and one with no offsets. Coincidentally, it also resamples the image to three-quarter size.
RescaleOpTest does the same using a fixed scale and no offsets.
RescaleTest scales all bands of an image between zero and two with no offsets.
As noted in the API, the scale and offset are applied to each band as the slope and y-intercept, respectively, of a linear function.
dstElement = (srcElement*scaleFactor) + offset

Basic logic is take RGB value of each pixel ,add some factor to it,set it again to resulltant matrix(Buffered Image)
import java.io.*;
import java.awt.Color;
import javax.imageio.ImageIO;
import java.io.*;
import java.awt.image.BufferedImage;
class psp{
public static void main(String a[]){
try{
File input=new File("input.jpg");
File output=new File("output1.jpg");
BufferedImage picture1 = ImageIO.read(input); // original
BufferedImage picture2= new BufferedImage(picture1.getWidth(), picture1.getHeight(),BufferedImage.TYPE_INT_RGB);
int width = picture1.getWidth();
int height = picture1.getHeight();
int factor=50;//chose it according to your need(keep it less than 100)
for (int y = 0; y < height ; y++) {//loops for image matrix
for (int x = 0; x < width ; x++) {
Color c=new Color(picture1.getRGB(x,y));
//adding factor to rgb values
int r=c.getRed()+factor;
int b=c.getBlue()+factor;
int g=c.getGreen()+factor;
if (r >= 256) {
r = 255;
} else if (r < 0) {
r = 0;
}
if (g >= 256) {
g = 255;
} else if (g < 0) {
g = 0;
}
if (b >= 256) {
b = 255;
} else if (b < 0) {
b = 0;
}
picture2.setRGB(x, y,new Color(r,g,b).getRGB());
}
}
ImageIO.write(picture2,"jpg",output);
}catch(Exception e){
System.out.println(e);
}
}}

Java bitmap font: blitting 1-bit image with different colors

I'd like to implement a simple bitmap font drawing in Java AWT-based application. Application draws on a Graphics object, where I'd like to implement a simple algorithm:
1) Load a file (probably using ImageIO.read(new File(fileName))), which is 1-bit PNG that looks something like that:
I.e. it's 16*16 (or 16*many, if I'd like to support Unicode) matrix of 8*8 characters. Black corresponds to background color, white corresponds to foreground.
2) Draw strings character-by-character, blitting relevant parts of this bitmap to target Graphics. So far I've only succeeded with something like that:
int posX = ch % 16;
int posY = ch / 16;
int fontX = posX * CHAR_WIDTH;
int fontY = posY * CHAR_HEIGHT;
g.drawImage(
font,
dx, dy, dx + CHAR_WIDTH, dy + CHAR_HEIGHT,
fontX, fontY, fontX + CHAR_WIDTH, fontY + CHAR_HEIGHT,
null
);
It works, but, alas, it blits the text as is, i.e. I can't substitute black and white with desired foreground and background colors, and I can't even make background transparent.
So, the question is: is there a simple (and fast!) way in Java to blit part of one 1-bit bitmap to another, colorizing it in process of blitting (i.e. replacing all 0 pixels with one given color and all 1 pixels with another)?
I've researched into a couple of solutions, all of them look suboptimal to me:
Using a custom colorizing BufferedImageOp, as outlined in this solution - it should work, but it seems that it would be very inefficient to recolorize a bitmap before every blit operation.
Using multiple 32-bit RGBA PNG, with alpha channel set to 0 for black pixels and to maximum for foreground. Every desired foreground color should get its own pre-rendered bitmap. This way I can make background transparent and draw it as a rectangle separately before blitting and then select one bitmap with my font, pre-colorized with desired color and draw a portion of it over that rectangle. Seems like a huge overkill to me - and what makes this option even worse - it limits number of foreground colors to a relatively small amount (i.e. I can realistically load up and hold like hundreds or thousands of bitmaps, not millions)
Bundling and loading a custom font, as outlined in this solution could work, but as far as I see in Font#createFont documentation, AWT's Font seems to work only with vector-based fonts, not with bitmap-based.
May be there's already any libraries that implement such functionality? Or it's time for me to switch to some sort of more advanced graphics library, something like lwjgl?
Benchmarking results
I've tested a couple of algorithms in a simple test: I have 2 strings, 71 characters each, and draw them continuously one after another, right on the same place:
for (int i = 0; i < N; i++) {
cv.putString(5, 5, STR, Color.RED, Color.BLUE);
cv.putString(5, 5, STR2, Color.RED, Color.BLUE);
}
Then I measure time taken and calculate speed: string per second and characters per second. So far, various implementation I've tested yield the following results:
bitmap font, 16*16 characters bitmap: 10991 strings / sec, 780391 chars / sec
bitmap font, pre-split images: 11048 strings / sec, 784443 chars / sec
g.drawString(): 8952 strings / sec, 635631 chars / sec
colored bitmap font, colorized using LookupOp and ByteLookupTable: 404 strings / sec, 28741 chars / sec

You might turn each bitmap into a Shape (or many of them) and draw the Shape. See Smoothing a jagged path for the process of gaining the Shape.
E.G.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import java.util.Random;
/* Gain the outline of an image for further processing. */
class ImageShape {
private BufferedImage image;
private BufferedImage ImageShape;
private Area areaOutline = null;
private JLabel labelOutline;
private JLabel output;
private BufferedImage anim;
private Random random = new Random();
private int count = 0;
private long time = System.currentTimeMillis();
private String rate = "";
public ImageShape(BufferedImage image) {
this.image = image;
}
public void drawOutline() {
if (areaOutline!=null) {
Graphics2D g = ImageShape.createGraphics();
g.setColor(Color.WHITE);
g.fillRect(0,0,ImageShape.getWidth(),ImageShape.getHeight());
g.setColor(Color.RED);
g.setClip(areaOutline);
g.fillRect(0,0,ImageShape.getWidth(),ImageShape.getHeight());
g.setColor(Color.BLACK);
g.setClip(null);
g.draw(areaOutline);
g.dispose();
}
}
public Area getOutline(Color target, BufferedImage bi) {
// construct the GeneralPath
GeneralPath gp = new GeneralPath();
boolean cont = false;
int targetRGB = target.getRGB();
for (int xx=0; xx<bi.getWidth(); xx++) {
for (int yy=0; yy<bi.getHeight(); yy++) {
if (bi.getRGB(xx,yy)==targetRGB) {
if (cont) {
gp.lineTo(xx,yy);
gp.lineTo(xx,yy+1);
gp.lineTo(xx+1,yy+1);
gp.lineTo(xx+1,yy);
gp.lineTo(xx,yy);
} else {
gp.moveTo(xx,yy);
}
cont = true;
} else {
cont = false;
}
}
cont = false;
}
gp.closePath();
// construct the Area from the GP & return it
return new Area(gp);
}
public JPanel getGui() {
JPanel images = new JPanel(new GridLayout(1,2,2,2));
JPanel gui = new JPanel(new BorderLayout(3,3));
JPanel originalImage = new JPanel(new BorderLayout(2,2));
final JLabel originalLabel = new JLabel(new ImageIcon(image));
originalImage.add(originalLabel);
images.add(originalImage);
ImageShape = new BufferedImage(
image.getWidth(),
image.getHeight(),
BufferedImage.TYPE_INT_RGB
);
labelOutline = new JLabel(new ImageIcon(ImageShape));
images.add(labelOutline);
anim = new BufferedImage(
image.getWidth()*2,
image.getHeight()*2,
BufferedImage.TYPE_INT_RGB);
output = new JLabel(new ImageIcon(anim));
gui.add(output, BorderLayout.CENTER);
updateImages();
gui.add(images, BorderLayout.NORTH);
animate();
ActionListener al = new ActionListener() {
public void actionPerformed(ActionEvent ae) {
animate();
}
};
Timer timer = new Timer(1,al);
timer.start();
return gui;
}
private void updateImages() {
areaOutline = getOutline(Color.BLACK, image);
drawOutline();
}
private void animate() {
Graphics2D gr = anim.createGraphics();
gr.setColor(Color.BLUE);
gr.fillRect(0,0,anim.getWidth(),anim.getHeight());
count++;
if (count%100==0) {
long now = System.currentTimeMillis();
long duration = now-time;
double fraction = (double)duration/1000;
rate = "" + (double)100/fraction;
time = now;
}
gr.setColor(Color.WHITE);
gr.translate(0,0);
gr.drawString(rate, 20, 20);
int x = random.nextInt(image.getWidth());
int y = random.nextInt(image.getHeight());
gr.translate(x,y);
int r = 128+random.nextInt(127);
int g = 128+random.nextInt(127);
int b = 128+random.nextInt(127);
gr.setColor(new Color(r,g,b));
gr.draw(areaOutline);
gr.dispose();
output.repaint();
}
public static void main(String[] args) throws Exception {
int size = 150;
final BufferedImage outline = javax.imageio.ImageIO.read(new java.io.File("img.gif"));
ImageShape io = new ImageShape(outline);
JFrame f = new JFrame("Image Outline");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(io.getGui());
f.pack();
f.setResizable(false);
f.setLocationByPlatform(true);
f.setVisible(true);
}
}
I have to figure there is a factor of ten error in the FPS count on the top left of the blue image though. 50 FPS I could believe, but 500 FPS seems ..wrong.

Okay, looks like I've found the best solution. The key to success was accessing raw pixel arrays in underlying AWT structures. Initialization goes something like that:
public class ConsoleCanvas extends Canvas {
protected BufferedImage buffer;
protected int w;
protected int h;
protected int[] data;
public ConsoleCanvas(int w, int h) {
super();
this.w = w;
this.h = h;
}
public void initialize() {
data = new int[h * w];
// Fill data array with pure solid black
Arrays.fill(data, 0xff000000);
// Java's endless black magic to get it working
DataBufferInt db = new DataBufferInt(data, h * w);
ColorModel cm = ColorModel.getRGBdefault();
SampleModel sm = cm.createCompatibleSampleModel(w, h);
WritableRaster wr = Raster.createWritableRaster(sm, db, null);
buffer = new BufferedImage(cm, wr, false, null);
}
#Override
public void paint(Graphics g) {
update(g);
}
#Override
public void update(Graphics g) {
g.drawImage(buffer, 0, 0, null);
}
}
After this one, you've got both a buffer that you can blit on canvas updates and underlying array of ARGB 4-byte ints - data.
Single character can be drawn like that:
private void putChar(int dx, int dy, char ch, int fore, int back) {
int charIdx = 0;
int canvasIdx = dy * canvas.w + dx;
for (int i = 0; i < CHAR_HEIGHT; i++) {
for (int j = 0; j < CHAR_WIDTH; j++) {
canvas.data[canvasIdx] = font[ch][charIdx] ? fore : back;
charIdx++;
canvasIdx++;
}
canvasIdx += canvas.w - CHAR_WIDTH;
}
}
This one uses a simple boolean[][] array, where first index chooses character and second index iterates over raw 1-bit character pixel data (true => foreground, false => background).
I'll try to publish a complete solution as a part of my Java terminal emulation class set soon.
This solution benchmarks for impressive 26007 strings / sec or 1846553 chars / sec - that's 2.3x times faster than previous best non-colorized drawImage().

Painting pixels images in Java

Which method is the best way to create a pixel image with java.
Say, I want to create a pixel image with the dimensions 200x200 which are 40.000 pixels in total. How can I create a pixel from a random color and render it at a given position on a JFrame.
I tried to create a own component which just creates pixel but it seems that this is not very performant if I create such a pixel a 250.000 times with a for-loop and add each instance to a JPanels layout.
class Pixel extends JComponent {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getRandomColor());
g.fillRect(0, 0, 1, 1);
}
}

You do not need to create a class for this. Java already has the excellent BufferedImage class that does exactly what you need. Here is some pseudo-code:
int w = 10;
int h = 10;
int type = BufferedImage.TYPE_INT_ARGB;
BufferedImage image = new BufferedImage(w, h, type);
int color = 255; // RGBA value, each component in a byte
for(int x = 0; x < w; x++) {
for(int y = 0; y < h; y++) {
image.setRGB(x, y, color);
}
}
// Do something with image

The key here is the Canvas class. It is the standard Component that allows arbitrary draw operations. In order to use it, you must subclass the Canvas class and override the paint(Graphics g) method, then loop through each pixel and draw your random color. The following code should work:
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;
import javax.swing.JFrame;
public class PixelCanvas extends Canvas {
private static final int WIDTH = 400;
private static final int HEIGHT = 400;
private static final Random random = new Random();
#Override
public void paint(Graphics g) {
super.paint(g);
for(int x = 0; x < WIDTH; x++) {
for(int y = 0; y < HEIGHT; y++) {
g.setColor(randomColor());
g.drawLine(x, y, x, y);
}
}
}
private Color randomColor() {
return new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(WIDTH, HEIGHT);
frame.add(new PixelCanvas());
frame.setVisible(true);
}
}
The generated image looks like this:

You'll probably want to create a BufferedImage of the size you want, and use img.setRGB(x, y, getRandomColor()) to create a bunch of random pixels. Then you could render the whole image wherever you want it.