I'm making a game in Java and I have it so that when the player presses the left arrow button, three images are drawn one after the other. But when the third image is drawn, you can still see the image drawn before it (I rotated the images to make it look more realistic). Is there anyway to "undraw" the images? I've done some research and haven't found anything specific.
No, you can't undraw an image. It sounds like the images aren't fully opaque.
Not to be an over-complication junkie, but how about using OpenGL to draw them on quads. That way you can hide, show, rotate, animate, accelerate etc so much easier. And it will all be tons faster than with Swing/AWT. JOGL library + NeHe Tutorials will quickly show you how to achieve this (really, you only need this and this). Or use Unity if you wanna do it even simpler and more portable.
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I am new to computer vision but I am trying to code an android app which does the following:
Get the live camera preview and try to detect one logo in that (i have the logo in my resources). In real-time. Draw a rect around the logo if found. If there is no match, dont draw the rectangle.
I already tried a couple of things including template-matching and feature detection using ORB.
Why that didnt work:
Template-matching:
Issues with scaling and rotation. I tried a multi scale variant of it but a) the performance was really bad and b) the rectangle was of course always shown trying to search for the image. There was no way to actually confirm in the code if the logo was found or not.
ORB feature detection:
Also pretty slow (5-6 fps) but it worked ok-ish. The other problem was that also i never could be sure if the logo was in the picture or not. ORB found random matches even if the logo was not in the picture.
Like I said, I am very new to this. I would appreciate the help on what would be the best way to achieve:
Confirm if a picture A (around 200x200 pixels) is in ROI of camera picture (around 600x600 pixels).
This shouldnt take longer than 50ms per frame. I dont know if thats even possible though. So if a correct way to do this would take a bit longer than that, I would just do the work in a seperate thread and only analyze like every fifth camera frame or so.
Would appreciate any hints or code examples on how to achieve that. Thank you!
With logo detection, I would highly recommend using OpenCV HaarClassifier. It is easy to generate training samples from a collection of images of the logo, or one logo image with many distortions.
If you can use a few rules like the minimum and maximum size of the logo to be detected, and possible regions on the image where it can appear, you can run the detector at a speed better than you mention with ORB.
I have been trying to "cut" an image for some time now, I ll explain why and what I tried.
So I wanted to create an hp "bar" except it's not a bar but a heart and so I though it would be easy all I had to do is have two pictures draw them on top of each other and then just cut one to make it appear as in hp was being lost, but I was not able to find a way to cut the image.
Setting the height just resizes the image as you might have guessed
I tried using textureRegion to kind of hack it but it didn't go so well
I found a method called clip begin which also uses scissors but for some reason that just doesn't seem to be working.
I might be using the clip begin wrong but I can't really find any real documentation on it, all I'm doing is:
image.clipBegin(x,y,height,weight);
image.clipEnd();
I almost forgot, I'm using a scene2d Image, might be a better way to go around it but not sure what that would be.
I would appreciate any ideas on how to do this, thank you.
You want to use the OpenGL Scissor support that Libgdx exposes. See the Libgdx Clipping wiki
and the Libgdx ScissorStack documentation.
The API isn't particularly friendly (its designed to support dynamically pushing multiple constraining rectangles, which as far as I've seen, isn't used very often).
The important point to remember with the scissor stack is that it only applies to actual draw commands that get issued. Since most APIs try to batch up draw commands, this means actual drawing might not happen when it looks like it should happen. To ensure clipping is happening you must flush any buffered draws before pushing the scissor (otherwise the wrong thing might get clipped) and you must flush any draw calls before popping the scissor (otherwise things you want clipped might avoid the scissors).
See libgdx ScissorStack not working as expected or libGDX - How to clip or How to draw on just a portion of the screen with SpriteBatch in libgdx? or Making a Group hide Actors outside of its bounds.
1) Re-Draw Vs Draw
Kind of a philosophical question, but... what is the "correct" or "accepted" way to render a game (2d, I understand how OGL perspecives work...) at different resolutions? Should I include separate sizes for my images (like Android APKs) and resize each object individually at draw on one canvas, or should I draw on a set-resolution drawing canvas, then resize that image onto another display canvas? I'm speaking generally, but, if you need me to be specific I'm using Java to build the engine.
Foreseeable benefits/issues:
#1) Resize at Draw
+ No additional drawing step
+ Sweet resolution
- Possible math/physics/placement issues
- Tons of math each step for scale
- Lots of resources
#2) Resize at Render
+ No additional math; one step
+ One set of images; smaller res. package
+ One set canvas size (easier to do math/phys./placement)
- Additional drawing step
- Poor resolution =(
It would seem that #2 is the obvious choice because of the number of benefits vs issues, but... is it? Is there a standard way to resize 2D games?
2) JOGL + Java2D + Java Swing
Would it be cumbersome to use JOGL, Java2D, and Java Swing at the same time? Would it be worth it to do 2D or layouts in JOGL? Why or why not?
EDIT: Using a BufferedImage to draw on and rendering the BufferedImage to the size of the panel with respect to aspect ratio is incredibly inefficient in swing. Apparently it's better to draw immediately to the panel, while resizing each image/element individually. Not my first hypothesis...
EDIT 2: Silly me... just scale and translate the graphics context to the size of the adjusted resolution before any other operations. The performance boost is super-dooper awesome. THIS is the correct answer to the question. DRAW ONCE, to scale/translation. B)
I can't answer your second question fully as I do not have much experience with JOGL or Java2D, but I don't see any reason for them to ever conflict or be cumbersome.
For your first question, I can definitely say that it depends. What's your target audience? Is your game memory intensive (Ever notice that many games have a high res/low res option)? Is this a game that will be available for vastly different screen sizes? If so you might want to provide 2-3 different "packages" of your assets, each scaled at a different size of the original (the largest one). The math to draw the images isn't as much as you think.
In addition:
If you build the game the right way, you wouldn't have to do much math at all. If you have some sort of Camera class that takes care of the viewing of your GameWorld then you simply have to scale the Camera's image instead of scaling each image independently.
I am developing a game using libgdx. Now i'd like to have a Background all over my map (Map size is not fixed yet i'll decide later). My map is tile based but i don't use TiledMaps. So i create and load the map with own code/editor.
My question now: How should i implement the background thing?
I thought about different ways:
Loading a huge Image, which covers all the map. This is not realy good cause i render things, which are not in my viewport (80 Tiles X,50 Tiles Y).
Deviding the Image in 4 or more Images and loading the one in the viewport. The Problem: At some point maybe part of all Images is in viewport so all Images are sent to GPU right?
Having 1 Image which cover the viewport (80,50) and follows the camera. Best performance i think, but it will look stupid...
Or every tile has an own Image and the Objects are drawn above them. Notice that i only render Tiles inside the viewport. But on Gamestart it would need to load Information about every tile in the level.
For Information: My Game is Topdown and the Background Shows the floor so no detailed hills etc are needed, just maybe some simple desert sand look and things like that. Is there another even better way?
What would be the best way for performance and optic?
If your game is Tile Based. It would make much more sense to have the background tiled aswell. Just use another layer for it. If your editor/loader does not support multiple layers, then I would recommend you to switch to another one, or add those features to it (if possible).
The Background Shows the floor so no detailed hills etc are needed, just maybe some simple desert sand look and things like that.
It is very easy to reuse tiles in something like a desert, because all their tiles are very similar (sand).
I'm trying to make a simple java game.
I have some png file that i want to draw, but first i want to make some modification on that png. I would like to take a png, and delete to background some parts of it and add some colored lines..
For my game im using libgdx.
I dont know what to use for this, so i can search on google about it and learn.
Few hints, about what functions i should use could be awesome, Ty.
P.S. I tryed to search on internet before post here, but i didnt find something that could help me, probably idk what to search.v
Edit:
I found Pixmap from libgdx, but i can delete to background. Any advices ?
Edit2:
i want to load this texture
multiplicate when needed (no problem here)
and delete some parts of it, to background, so it will take this shape:
by using pixmap, when im drawing background over it, nothing is happen, because its draw over, not instead of.
What i could make, was using pixmap to draw the top part, that i want to delete, and manualy delete it using external programs:
I think you might want to look at a "mask" image. There are some approaches listed here: https://github.com/mattdesl/lwjgl-basics/wiki/LibGDX-Masking
Alternatively, you could use create a mesh that encodes the "ground" (with the bump) and then texture it. OpenGL would take care of truncating the edge of the mesh. Try: Drawing textured polygons with libgdx
Another approach is to just draw the dirt texture on the full screen, and then draw the "background" over it. You will need to make pixels in the "background" image transparent so the dirt will show through. Whatever pixel editor you are using should be able to do that. Alternatively, pick a "key" color and convert those pixels to transparent when you load the image as a pixmap.
I don't know if this question is serious, but you cannot do what you're asking in Java. You need a photo editing software such as Photoshop or GIMP.