My question involves the drawImage method in Java Graphics2D (this is for a desktop app, not Android).
My BufferedImage that I'd like to draw contains high resolution binary data, most pixels are black but I have some sparse green pixels (the green pixels represent data points from an incoming raw data stream). The bitmap is quite large, larger than my typical panel size. I made it large so I could zoom in and out. The problem is when I zoom out I lose some of my green pixels .. as an example if my image is 1000 pixels and by panel is 250 pixels, I'd lose 1 out of 4 pixels in each direction (X and Y). If I use nearest neighbor interpolation when I scale the pixels can just disappear to black. If I use something like bilinear interpolation my green pixel will get recolored to somewhere between black and green.
I understand all this behavior, but my question is that is there any way to get the behavior I want, which is to make sure if any pixels is non-black I want it to be drawn at it's full intensity. Perhaps something like a "max-hold" interpolation.
I realize I could probably do what I want by drawing shape primitive over a black background, and maybe this is what I'll have to do. But there is a reason I'm using bitmaps (has to do with the fact that I'm showing the data in a falling spectrogram-type display - and it does have a mode where all the pixels could be colored and not just black and green).
Thanks,
You could look at the implementation of drawImage and override it to get your desired behaviour, however probably the core of the scaling uses hardware acceleration, so re implementing it in Java would be really slow.
You could look into JOGL, but my impression is that, if your pixels are really sparse, just drawing the green pixels on a black background (or over an image) would be both easy to code and very fast.
You could even have an heuristic switching between painting the dots to scaling the image if the number of dots starts being too high.
Related
I am using libGDX to make a small game, I made a little sprite (32x32) that is shown in the center of the screen. For some reason when I render the texture to the screen it loses its quality. Since the textures are so small I made the screen width and height 200 and 100 respectively. Any tips or answers would be much appreciated.
Your sprite (32x32) needs to be displayed on an area which is larger than 32x32, meaning that the image needs to be upscaled and interpolated (i.e. pixels between the 32 known ones need to be calculated). A common approach is smooth (often times linear) interpolation to fill in the additional pixels, which works well for photorealistic textures; it appears to have occurred here.
For pixel-art, you likely want "nearest-neighbor" interpolation instead. While the exact way to set it depends on the structure of your code, you may be able to do something like:
textureObject.setFilter(TextureFilter.Nearest, TextureFilter.Nearest);
I'm drawing to a Canvas using Graphics through a BufferStrategy with lines such as
g.drawImage(bufferedImage, x, y, null);
I currently have this running undecorated in a JFrame, 1920x1080p as per the resolution of my laptop. I'm curious as to whether there is any way to alter the resolution of the Graphics rendered, particularly lowering resolution so as to increase efficiency/speed, or fitting to another differently sized screen. There are many objects being rendered with a camera and the game runs fairly well, but any usable alterations to the resolution would be useful as optional in my settings.
I've researched this and found no good answers. Thank you for your time.
(Resolution changes such as for printing.)
Best to use a drawImage with a smaller image, and scaled width and height.
Now, you could even render all in your own BufferedImage using a Graphics2D with BufferedImage.createGraphics and scale afterwards. Not so nice for text or printing.
Or use Graphics2D scaling:
For complex rendering:
g.scale(2.0, 2.0);
... // Draw smaller image
g.scale(0.5, 0.5);
As you might imagine this probably does not help in memory consumption, apart from needing smaller images. At one point all pixels of the image must be given in the devices color size. 256 colors gif, or 10KB jpg will not help.
The other way around, supporting high resolutions with tight memory also exists. There one might use tiled images, see ImageIO.
Important is to prepare the image outside the paintComponent/paint.
You might also go for device compatible bit maps if you make your own BufferedImage, but this seems circumstantial (GraphicsEnvironment).
I'm using slick2d to render an Animation, but using anti-aliasing
Without AA, the movement is choppy, as one would expect for something without AA.
I turn on AA in my game's preRenderState with:
g.setAntiAlias(true);
This leads to:
Note the diagonal line in the center, presumably caused by the two triangles that render the rectangle not meeting precicely. How can I remove that while still using AA to smooth my movement? I found http://www.java-gaming.org/index.php?topic=27313.0 but the solution was "remove AA" which I am reluctant to do.
This looks suspiciously like artifacts due to GL_POLYGON_SMOOTH.
When you use that (deprecated) functionality, you are expected to draw all opaque geometry with blending enabled and the blend function: GL_SRC_ALPHA_SATURATE, GL_ONE. Failure to do so produces white outlines on most contours (aliased edges, basically).
Chapter 6 of the OpenGL Redbook states:
Now you need to blend overlapping edges appropriately. First, turn off the depth buffer so that you have control over how overlapping pixels are drawn. Then set the blending factors to GL_SRC_ALPHA_SATURATE (source) and GL_ONE (destination). With this specialized blending function, the final color is the sum of the destination color and the scaled source color; the scale factor is the smaller of either the incoming source alpha value or one minus the destination alpha value.
This means that for a pixel with a large alpha value, successive incoming pixels have little effect on the final color because one minus the destination alpha is almost zero. With this method, a pixel on the edge of a polygon might be blended eventually with the colors from another polygon that's drawn later. Finally, you need to sort all the polygons in your scene so that they're ordered from front to back before drawing them.
That is a lot of work that almost nobody does correctly when they try to enable GL_POLYGON_SMOOTH.
Every time you enable anti-aliasing in Slick2D, it should look like this.
g.setAntiAlias(true);
GL11.glBlendFunc(GL11.GL_SRC_ALPHA_SATURATE, GL11.GL_ONE);
Basically same as Andon's answer, but with code that should solve the problem.
Note that with this whatever you draw first will be on top, rather than what you draw last. So you may need to reverse rendering order.
I am generating very large hex grids (up to 120k total hexes at 32px wide hexes results in over 12k wide images) and I'm trying to find an efficient way to bind these to OpenGL textures in libgdx. I was thinking of using multiple FBOs and breaking the grid up as necessary into tiles, but I'm not sure how to ensure continuity between the FBOs. I can't start with one massive FBO, because that is backed up by a texture so it would fail from trying to load it to video memory. I can't use a standard bitmap on the heap because I need the drawing functionality of an OpenGL surface.
So what I was thinking was I would need to overdraw on the FBOs and somehow pick up on the next FBO exactly where the previous left off. However I'm not sure how to go about this. I'm drawing the hex grid with a series of hexagonal meshes, FYI.
Of course, there's probably some other much simpler and more efficient way to do this that I'm not even thinking of, which is why I pose this question to you fine people!
You have to draw it in pieces. You need to be able to draw your hex grid from an arbitrary position. This means being able to compute which hexes to draw based on a rectangle overlaid over the map. This isn't a hard problem, and I wouldn't worry too much about drawing extra stuff off-screen. You should master this ability to view the hexmap from any position before moving on.
Once you've mastered that, it's really simple.
Draw the top-left corner and store the pixel data. Then move the area you're drawing over exactly one image width. Draw and store that. Move the area over one image width. Draw and store it. Keep doing that until you've covered the entire width.
Move down one image height and repeat the process. Once you've run out of width and height, you're done. Save your mega-huge image.
You don't need FBOs for this. You could draw it to the screen if you wanted. Though if you want maximum performance, I would suggest using FBOs, double buffering them, and using glReadPixels though a pixel buffer object. That should cut down a lot on latency.
I'm trying to write a graphical effect where a circle moves around an image smudging the image as it goes (like the way the smudge tool in Gimp or Photoshop would work). The basic algorithm I'm using is:
the circle moves from position A to position B on the bitmap
copy a circle of pixels from position A into a temporary bitmap
draw this circle of pixels from the temporary bitmap to position B using alpha of about 50%.
This works fine and looks like what I would expect, where the image will look like it's getting smudged if the circle moves 1 pixel at a time over the image.
I now want to add some texture to the smudge effect. I have a bitmap that contains a picture of a paint blob. The algorithm from the above is modified to the following so the smudge takes the shape of this paint blob:
as before
replace the temporary bitmap pixels with the paint blob texture then copy the circle of pixels from position A into the temporary bitmap but only keep the pixels that match up against paint blob pixels (i.e. use Porter-Duff "source in destination" mode when drawing the circle into the temporary bitmap).
as before
This almost works and it looks like it's fine initially but gradually the smudging makes the colors in my image darker! If the circle passes over the same area several times, the colors eventually change to black. Any ideas what I could be doing wrong?
I've implemented the above in Android. I happened upon this post about bitmaps in Android (like my paint blob texture) being loaded with "premultiplied alpha", where the author says it caused his images to become darker because of it:
http://www.kittehface.com/2010/06/androidbitmap-and-premultiplied-alpha.html
I suspect I'm suffering from a similar problem but I don't understand what's going on well enough and don't know how to fix it. Does anyone have hints at what might be going on?
Well from first glance the reason the image is getting darker is because #3 in the first three steps. You overlaying a pixel over an existing pixel at 50%. You might want to consider using the mean of the original pixel value and the new pixel value. You might want to research some blurring algorithms.