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Index › Programming Questions & Help › Syntax Questions › loadBytes() vs. loadImage()
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loadBytes() vs. loadImage() (Read 632 times)
ilteris
loadBytes() vs. loadImage()
Apr 9th, 2006, 10:54pm  
Mighty List,

I am trying to load an image to my applet with loadBytes but it simply doesn't load (gives me out of bounds error). The image format is jpeg. Contrary when I try to load a raw image file it loads without any problems. Why?

Code:

byte input[];
byte output[];

int imgWidth;
int imgHeight;
int imgNumPixels;

void setup() {
  imgWidth = 200;
  imgHeight = 150;
  imgNumPixels = imgWidth * imgHeight;

  input = loadBytes("deneme.jpg"); // deneme.raw loads
  output = new byte[imgNumPixels];

  size(200,150);
  background(0);
}

void draw () {
  loadPixels();

  for(int i=0; i<imgWidth; i++) { 
    for(int j=0; j<imgHeight; j++) { 
	pixels[i*imgWidth + j] = color(input[i*imgWidth + j] & 0xFF); 
    } 
  } 
  updatePixels();

}
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mark hill
Re: loadBytes() vs. loadImage()
Reply #1 - Apr 9th, 2006, 11:10pm  
loadBytes will take the compressed .jpg data in, which of course will throw an array index out of bounds error when you try to access, as it is not as large as indicated by imgNumPixels.

Insert this code to see the difference:


Code:

  input = loadBytes("deneme.jpg"); // deneme.raw loads
  println(input.length);
  println(imgNumPixels);


LoadImage is decompressing the file to its correct size.
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ilteris
Re: loadBytes() vs. loadImage()
Reply #2 - Apr 9th, 2006, 11:57pm  
that makes sense! yes you are right, they are outputting different numbers, so my question is: what should i do in order to load an jpeg through loadBytes() ?

ty
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mark hill
Re: loadBytes() vs. loadImage()
Reply #3 - Apr 10th, 2006, 12:03am  
Well aside from using loadImage, you'll need a .jpeg decoder

like this:

http://java.sun.com/j2se/1.5.0/docs/guide/2d/api-jpeg/com/sun/image/codec/jpeg/JPEGImageDecoder.html

Any reason for not using loadImage?
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ilteris
Re: loadBytes() vs. loadImage()
Reply #4 - Apr 10th, 2006, 12:08am  
thanks for the headsup Mark!

nope not really, I just want to understand in and out that's all. I think I am almost there. I was trying to get the RGB sum of an image and I succeeded it. Here is my code:

Code:

PImage b;
void setup() {
  b = loadImage("deneme.jpg");
  int rsum = 0;
  int gsum = 0;
  int bsum = 0;

  for (int i = 0; i <b.pixels.length; i++) {

    byte redk = (byte) ((b.pixels[i]   &  0xFF0000) >> 16);
    // println("redk: "  + redk);
    byte greenk = (byte) ((b.pixels[i] &  0x00FF00) >> 8);
    // println("greenk: "  + greenk);
    byte bluek = (byte) ( b.pixels[i]  &  0x0000FF);
    // println("bluek: "  + bluek);
    
    rsum += redk;
    gsum += greenk;
    bsum += bluek;
  }
  println(rsum/b.pixels.length);
  println(gsum/b.pixels.length);
  println(bsum/b.pixels.length);
  size(200,150);
  image(b,0,0);
  //background(0);
}


now I am trying to convert this into HSB values, can you slap me in the right direction?


best
ilteris
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mark hill
Re: loadBytes() vs. loadImage()
Reply #5 - Apr 10th, 2006, 11:55am  
Try this, just hacked from various sources, so forgive any nastiness!

You'll need an image to work from, or you can generate a spectrum as you please.

This demonstrates:
the rgb (range 256)
our hsb (range 360.0, 100.0, 100.0) and java.awt.color.RGBtoHSB (range 1.0)

You can see the minor imperfections in the maths.

Code:


PImage rgb;

void setup() {
  size(320,200);
  
  rgb = loadImage("spectrum.jpg");
  image(rgb,0,0,320,200);
}

void draw () {
  
  
}

void mousePressed () {
  
  colorMode(RGB, 255);
  loadPixels();
  int col = pixels[mouseY*width+mouseX];
  int r = (col & 0xff0000) >> 16;
  int g = (col & 0x00ff00) >> 8;
  int b = (col & 0x0000ff);
  
  fill (r,g,b);
  rect (20, height/2, 20, 20);
  println("RGB- " + "r: " + r + " g: " + g + " b: " + b);
  
  colorMode(HSB, 360, 100, 100);
  float[] hsb = RGBtoHSB (r,g,b);
  fill (hsb[0], hsb[1], hsb[2]);
  rect (60, height/2, 20, 20);
  println ("myHSB- " + "h: " + hsb[0] + " s: " + hsb[1] + " b: " + hsb[2]);
  
  colorMode(HSB,1.0);  
  float[] jav = javaRGBtoHSB(r, g, b);
  fill (jav[0], jav[1], jav[2]);
  rect (100, height/2, 20, 20);
  println ("JavaHSB- " + "h: " + jav[0] + " s: " + jav[1] + " b: " + jav[2]);
}

 public float[] javaRGBtoHSB(int R, int G, int B) {
	float[] hsb = Color.RGBtoHSB(R, G, B, null);  
	return hsb;
    } 

float[] RGBtoHSB (int r, int g, int b) {
  
	  float[] hsb = new float[3];

	  hsb[2] = max(max(r,g),b);
float mymin = min(min(r,g),b);
hsb[1] = (hsb[2] <= 0) ? 0 : round(100*(hsb[2] - mymin)/hsb[2]);
hsb[2] = round((hsb[2] /255)*100);
hsb[0] = 0;

if((r == g) && (g == b)){
hsb[0] = 0;
}else if(r >= g && g >= b){
hsb[0] = 60*(g-b)/(r-b);
}else if(g >= r && r >= b){
hsb[0] = 60 + 60*(g-r)/(g-b);
}else if(g >= b && b >= r){
hsb[0] = 120 + 60*(b-r)/(g-r);
}else if(b >= g && g >= r){
hsb[0] = 180 + 60*(b-g)/(b-r);
}else if(b >= r && r >= g){
hsb[0] = 240 + 60*(r-g)/(b-g);
}else if(r >= b && b >= g){
hsb[0] = 300 + 60*(r-b)/(r-g);
}else{
hsb[0] = 0;
}
hsb[0] = Math.round(hsb[0]);	  
	  return hsb;
}
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