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How to create multicolor rasterized picture in processing

I followed this tutorial on Youtube, and I have successfully added colors to the black and white picture. However, my intention was to create a multi-color or gradient effect (like here or here) instead of switching colors when I move the cursor.
I very new at processing, and I have tried to play with the variable, with no success.
Here is the code snippet of the sketch:
`
PImage img;
void setup() {
size(598,336);
colorMode(HSB);
img = loadImage("picture-in-data-folder.jpg");
img.resize(598,336);
//ellipseMode(RADIUS);
frameRate(30);
}
void draw() {
background(255);
noStroke();
// fill(0);
float tiles = mouseX/10;
float tileSize = width/tiles;
// color section
fill(color(tiles, 255, 255));
tileSize++;
if (tiles > width / 2) {
tileSize = 0;
}
// end color section
translate(tileSize/2, tileSize/2);
for (int x = 0; x < tiles; x++) {
for (int y = 0; y < tiles; y++) {
color c = img.get(int(x*tileSize),int(y*tileSize));
float size = map(brightness(c), 0, 255, tileSize, 0);
ellipse(x*tileSize, y*tileSize, size, size);
// image(img, mouseX, mouseY);
}
}
}
I would be grateful if you had any hints, or if you could provide an advice.
Thanks.

Short answer: you need to put a fill() command inside the for loop.
Long answer:
Right now, your code is doing the following:
Define tiles based on mouseX
Set the fill color to (tiles, 255, 255)
Draw all the circles
I think what you want it to do is something like this:
Set the fill color to (21, 255, 255) (or whatever you want the first color to be)
draw the first circle
set the fill color to the next color in the gradient
draw the second circle
etc.
In order to do this, you need to put a command into the for loop which changes the fill color. Here is one way to do that:
for (int x = 0; x < tiles; x++) {
for (int y = 0; y < tiles; y++) {
color c = img.get(int(x*tileSize),int(y*tileSize));
float size = map(brightness(c), 0, 255, tileSize, 0);
fill(map(x, 0, tiles, 0, 255), 255, 255);
ellipse(x*tileSize, y*tileSize, size, size);
}
}
I just added that fill command as a function of x, but you can make it whatever you want. In order for it to be a gradient, it needs to vary somewhat with x or y.

Java Picture copy method

I have been working on this method in Picture.java for a programming course. The code is supposed to take an original image with a target image, x and y coordinates, and return a merged image with the original image pasted on these coordinates on the target image. A precondition is that the target image must have bigger dimensions than the original image. Here's the code I wrote:
public Picture copyPicture (Picture target, int startx, int starty)
{
Picture merged = new Picture(target);
for (int x = 0, mergx = startx; x < getWidth(); x++, mergx++)
{
for (int y = 0, mergy = starty; y < getHeight(); y++, mergy++)
{
Pixel orig = getPixel(x,y);
Pixel mergedPix = merged.getPixel(mergx, mergy);
mergedPix.setColor(orig.getColor());
}
}
return merged;
}
However, the method doesn't seem to work for me. I'm not sure what I did wrong, but nothing happens to either of the images. Can someone give me a tip?

Find first red pixel and crop picture

I want to find with OpenCV first red pixel and cut rest of picture on right of it.
For this moment I wrote this code, but it work very slow:
int firstRedPixel = mat.Cols();
int len = 0;
for (int x = 0; x < mat.Rows(); x++)
{
for (int y = 0; y < mat.Cols(); y++)
{
double[] rgb = mat.Get(x, y);
double r = rgb[0];
double g = rgb[1];
double b = rgb[2];
if ((r > 175) && (r > 2 * g) && (r > 2 * b))
{
if (len == 3)
{
firstRedPixel = y - len;
break;
}
len++;
}
else
{
len = 0;
}
}
}
Any solutions?

You can:
1) find red pixels (see here)
2) get the bounding box of red pixels
3) crop your image
The code is in C++, but it's only OpenCV functions so it should not be difficult to port to Java:
#include <opencv2\opencv.hpp>
int main()
{
cv::Mat3b img = cv::imread("path/to/img");
// Find red pixels
// https://stackoverflow.com/a/32523532/5008845
cv::Mat3b bgr_inv = ~img;
cv::Mat3b hsv_inv;
cv::cvtColor(bgr_inv, hsv_inv, cv::COLOR_BGR2HSV);
cv::Mat1b red_mask;
inRange(hsv_inv, cv::Scalar(90 - 10, 70, 50), cv::Scalar(90 + 10, 255, 255), red_mask); // Cyan is 90
// Get the rect
std::vector<cv::Point> red_points;
cv::findNonZero(red_mask, red_points);
cv::Rect red_area = cv::boundingRect(red_points);
// Show green rectangle on red area
cv::Mat3b out = img.clone();
cv::rectangle(out, red_area, cv::Scalar(0, 255, 0));
// Define the non red area
cv::Rect not_red_area;
not_red_area.x = 0;
not_red_area.y = 0;
not_red_area.width = red_area.x - 1;
not_red_area.height = img.rows;
// Crop away red area
cv::Mat3b result = img(not_red_area);
return 0;
}

This is not the way to work with computer vision. I know this, because I did it the same way.
One way to achieve your goal would be to use template matching with a red bar that you cut out of your image, and thus locate the red border, and cut it away.
Another would be to transfer to HSV space, filter out red content, and use contour finding to locate a large red structure, as you need it.
There are plenty of ways to do this. Looping yourself over pixel-values rarely is the right approach though, and you won't take advantage of sophisticated vectorisation or algorithms that way.

Fill not-transparent part of image by color

I have one task in Libgdx:
Change color of image for example triangle,star, heart and others shapes.
All shapes are given in png with transparent background.
I'm doing this with Pixmap, checking every pixel if it is not-transparent fill pixel with needed color.
Here is the code:
for (int y = 0; y < pixmap.getHeight(); y++) {
for (int x = 0; x < pixmap.getWidth(); x++) {
Color color = new Color();
Color.rgba8888ToColor(color, pixmap.getPixel(x, y));
if(color.r != 1 || color.b != 1 && color.g != 1){
pixmap.setColor(setColor);
pixmap.fillRectangle(x, y, 1, 1);
}
}
}
Is there any other way to do this?
Because method below works too long.

You can certainly speed up the way you're doing it, because right now for every pixel in the image you are instantiating a new Color object and converting the pixel components into separate floats. And then the GC will have to take time to clear up all those Color objects you are generating. Those extra intermediate steps are unnecessary.
Also, you only need to call pixmap.setColor one time (although that is fairly trivial). And you can use drawPixel instead of fillRectangle to more efficiently draw a single pixel.
static final int R = 0xFF000000;
static final int G = 0x00FF0000;
static final int B = 0x0000FF00;
pixmap.setColor(setColor);
for (int y = 0; y < pixmap.getHeight(); y++) {
for (int x = 0; x < pixmap.getWidth(); x++) {
int pixel = pixmap.getPixel(x, y);
if((pixel & R) != R || (pixel & B) != B && (pixel & G) != G){
pixmap.drawPixel(x, y);
}
}
}
(By the way, did you mean to check red or blue and green? Seems like odd criteria unless you only want to change the color if the original color is pure yellow, cyan, or white.)
If you are merely drawing the images as Textures, then there is no need to be operating on the Pixmaps like this. You could make your source image white and tint the image when drawing it with SpriteBatch, for example, and this would have no impact on performance.

Support library provides utilities to tint drawable.
// create a drawable from the bitmap
BitmapDrawable tintedDrawable = DrawableCompat.wrap(new BitmapDrawable(getResources(), pixmap));
// Apply a Tint, it will color all non-transparent pixel
DrawableCompat.setTint(setColor);
// Draw it back on a bitmap
Bitmap b = Bitmap.createBitmap(pixmap.getWidth(), pixmap.getHeight(), Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
tintedDrawable.setBounds(0, 0, pixmap.getWidth(), pixmap.getHeight());
tintedDrawable.draw(c);

If you just need to show these pictures with a specific color in your application you can simply do it with setColorFilter
ImageView ivEx = (ImageView) findViewById(R.id.ivEx);
int color = Color.parseColor("your color's code");
ivEx.setColorFilter(color);

Random outofboundsexception being thrown for no reason?

I'm using LWJGL and Slick2D for a game I'm making. I can't seem to get it to draw the way I want it to be draw so I came up with an idea just to make my own drawing method. Basically it takes a image, a x, and a y and it goes through each pixel in the image, gets the color, then draws the image with the parameter x plus the x pixel it's on to get the position that the pixel is suppost to be drawn on. Same idea with the y. Although if the alpha channel isn't 255 for the pixel it doesn't draw it, although I'll fix that later. The problem is that whenever I run my code I get "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -2044". I'm really confused. I'm hoping someone can figure out why this is happening.
private void DrawImage(Image image, int xP, int yP)
{
//xP And yP Are The Position Parameters
//Begin Drawing Individual Pixels
glBegin(GL_POINTS);
//Going Across The X And The Y Coords Of The Image
for (int x = 1; x <= image.getWidth(); x++)
{
for (int y = 1; y <= image.getHeight(); y++)
{
//Define A Color Object
Color color = null;
//Set The Color Object And Check If The Color Is Completly Solid Before Rendering
if ((color = image.getColor(x, y)).a == 255)
{
//Bind The Color
color.bind();
//Draw The Color At The Coord Parameters And The X/Y Coord Of The Individual Pixel
glVertex2i(xP + x - 1, yP + y - 1);
}
}
}
glEnd();
}

My answer is assuming that the texture is an array of data.
I have a feeling it is the getColor() method. Your for loop runs through and will use the height and width values. An array usually starts off with 0 and width and height are just array counts typically. So I can see when you reach HEIGHT, that the texture array will throw an exception.
Try removing the <= part and replace it with <
EXAMPLE:
for (int x = 1; x < image.getWidth(); x++)
It may also help you to start off with zero so you can get the entire image.
EXAMPLE
for (int x = 0; x < image.getWidth(); x++)
Here is a link on arrays.
This way, when you ask for the color at whatever position, it will never ask for a color reaching beyond what is in the texture array. Hopefully I made sense.