Develop Reference

How do I make 2d- Flashlight effect in Processing 3

For reference the effect I'm going for is this:
I'm working in Processing 3, NOT p5.js.
I've looked around processing forums, but i can't find anything that works in the current version or doesn't use PGraphics and a mask which from what I've read can be expensive to use.
My current ideas and implementations have resulted to drawing shapes around the player and filling the gaps in with a circles with no fill that has a large stroke weight.
Does anyone know of any methods to easily and inexpensively draw a black background over everything except a small circular area?
If this is the wrong place to ask this question just send me on my way I guess, but please be nice. Thank you:)

You could create an image (or PGraphics) that consists of mostly black, with a transparent circle in it. This is called image masking or alpha compositing. Doing a Google image search for "alpha composite" returns a bunch of the images I'm talking about.
Anyway, after you have the image, it's just a matter of drawing it on top of your scene wherever the player is. You might also use the PImage#mask() function. More info can be found in the reference.

How to paint the portion of the image inside its border line via using libgdx?

I am creating an image painting app in libgdx where user would touch the portion of the image. e.g If the user touch the wheels of a car that should turn into the selected color.
I don't really know how to specify the custom area around the touch. That can be a wheel, a door which are not always rectangle and circle. I just need an idea to do it. Whether libgdx pixelmap can achive this. I have to paint the image inside the border line of the touch region. I hope my problem is clearly stated.
I woule really appreciate for your time for giving the answers. Thanks in advance

I think you want to look at flood fill algorithms. I don't think there is any built-in support for this in libGDX, but you should be able to implement your own flood fill on a libGDX pixmap.

Can i create "complex" gradients to achieve shadow on swing(x) components

I'd like to create shadow effects around my JComponent and especially around my JTextField's (JXTextField's since i use SwingX api).
I already know about the DropShadowBorder class from SwingX but it's not exactly what i want to achieve. I decided to do it myself by using rounded rectangle and gradients.
My idea is to create a rounded rectangle, apply a gradient to it and then draw the component on top of this rectangle with a given offset to create the shadow effect.
The problem is that i'm only aware of the GradientPaint class that allow me to specify start and end point of my gradient. Unless i'm wrong, i think i can't achieve this effect which such a gradient, i think i would need a gradient that start at the center and then fade toward the edges. Is there a way to do such a gradient with the actual API or do i need to write it myself?
Thanks.
EDIT: The is to do a text field that looks like:
The shadow is more important on the bottom than on the right and left sides.

There is no easy way to achieve exactly what you want.
To create an exact effect of such shadow you will have to do several things:
Paint a black/gray (color of your shadow) rounded rectanle on a separate image sized to component plus some additional spacing at the sides
Blur that image to create a shadow from the flat rounded rectangle
Render that image under the field by either using your own UI or just replacing field's paintComponent method
Let me explain each step a bit more:
You need a separate image so that the background/component won't get blurred together with the shadow. Plus you cannot apply any filter directly to the Graphics - you need an Image.
You can read a good explanation of how-to-blur here: http://www.jhlabs.com/ip/blurring.html
You need to place (paint) the shadow image before the component itself and that is possible in two ways: paint it on the panel/container that contains the field or replace the field paintComponent method or UI itself.

If you need a radial gradient, there is one: RadialGradientPaint
http://docs.oracle.com/javase/6/docs/api/java/awt/RadialGradientPaint.html
(You specify a center point and a radius here)
BTW, what's wrong with DropShadowBorder? (it is very similar to what you want, and you could always take the source code and modify it)

Best way to render and update an image each frame?

What is the best way to edit singular pixels of an texture multiple times per frame? I have tried using a couple ways to no avail. What is the most optimal way to do this? I have tried using Intermediate mode and drawing each quad, thought, this is really slow.
Edit:
I forgot to mention that I am doing an unusual "fog of war" system. This system doesn't let you see around walls but instead acts like a 2D ray traced shadow. I want these shadows to be pixelated as this is part of the style of the game. I am trying to find the best way to do a form of a shadow map that I can overlay over the world to show what you can see.

I recommend using a Pixel Buffer Object.

mouseListeners and JLabels using images with transparent pixels

I'm willing to make a isometric game but I'm having hard time with the mouseListener.
I'm using Swing and make losanges by using square images with transparent pixels (GIF format).
The problem is that making losanges touch each other edge means having the transparent pixels of one on the top of the others, which is a problem with the mouseListener.
I'm willing to know exactly which losange was clicked on, but as the transparent pixels of the nearby losange get on the top of the one that was clicked on, the wrong losange is selected as the KeyEvent source.
Is there a way to have mouseListener not considering transparent pixels as part of the shape ?
Thanks for reading.

It's not clear
1) why the tiles have to overlap, or
2) why you're using JLabels for the tiles
There's are many ways to solve the problem you're having, but I'd just make a single JComponent that renders the tiles as needed, and is the sole MouseListener.

As mentioned by Jonathan, I think you're using the wrong technology for the job. I've had great success using a 2D graphics framework for software such as this. In my case I'm a big fan of Piccolo. I know you don't want to hear this, but consider starting over with the appropriate toolset.