Draw segments of a bitmap using Canvas - java

I have a picture (resource) that I would like to use for my application in Android. But I only want to draw specific segments of it. My initial thought is to turn it into a bitmap and specify which pixels need to be drawn and where. I tried canvas.drawBitmap(bitmap, src, dst, null); but it doesn't seem to work. Maybe I am not using it right.
Just wondering if it is possible at all, and what can I use to achieve this?
Thanks!
src = new Rect(20,40,20,40);
dst = new Rect(20,40,20,40);
canvas.drawBitmap(background, offset, 0, null);
canvas.drawBitmap(bitmap, src, dst, null);
I was hoping to see the area specified at src's coordinates to be drawn into the area specified by dst's coordinates, but I don't see anything, other than the background.

dst should be where you want to draw the image in the canvas, and the src should be the Rect you want crop from.

You might want to use a format that supports an alpha channel or load the bitmap as well as a greyscale image for the alpha channel, construct an image from both and draw that. Try Java's Graphics2D object. Here's an article that should get you started.

Related

Libgdx get Texture from Image or Drawable

I would like to get the Texture data out of an image, so it may be rendered directly, but I see no straightforward way of making it, google searches show the other way around only.
I am able to get the Drawable, but the interface doesn't specify the exact texture data, so there's no way that I see to convert an Image actor into a Texture.
What I am trying to achieve is to have brushes, where the data of the brushes are stored in the image of an ImageButton. So upon clicking on an ImageButton The user would be able to draw on the screen based on the image stored in the buttons.
How might I be able to do that?
After digging deeper, I found a solution on the forums:
Your best bet is probably to draw your textures to a FrameBuffer with
a 1:1 scale, then you can use
ScreenUtils.getFrameBufferPixmap
To copy a pixmap off the FrameBuffer and resize as you wish.
Something like this:
fb.begin();
sb.begin();
sb.draw(texture, 0, 0);
sb.end();
Pixmap pm = ScreenUtils.getFrameBufferPixmap(0, 0, width, height);
fb.end();
It's not exactly a texture, but it is exactly what I would have needed: the pixel data extracted from a drawable.
After much thought I decided that it is easier to just store the texture data redundantly next to to the Imagebuttons, and query directly the stored data, instead of using the ImageButton as a kind of container, which it shouldn't be.

Rotation and collision is possible with fillrect() created rectangle?-j2me

I am working on a J2ME landscape game.I have created a rectangle using fillRect()
like this.
gr.fillRect(52,180,5,10);
Now I want to do rotation,and check collision with this rectangle.Is this possible?Is there any way to convert this fillrect() image to a sprite?
How can I manage it?
I have done it with immutable image.I used same coordinates as fillRect()
Image source; // the image to be copied
source = Image.createImage(...);
Image copy = Image
.createImage(source.getWidth(), source.getHeight());
Graphics g = copy.getGraphics();
g.drawImage(source, 0, 0, TOP|LEFT);
But it is impossible to rotate.

Alternatives to Canvas.snapshot() on JavaFX

I'm developing a little graphic engine using Canvas in JavaFX. In some point I had to render an off screen image, and then print it on my primary canvas using its GraphicContext.
I'm using this code right now:
private Canvas offScreenCanvas;
private GraphicsContext offScreenGraphic;
private SnapshotParameters parameters;
private WritableImage offScreenImage;
[...]
offScreenCanvas = new Canvas(WIDTH, HEIGHT);
offScreenGraphic = offScreenCanvas.getGraphicsContext2D();
parameters = new SnapshotParameters();
parameters.setFill(Color.TRANSPARENT);
[...]
offScreenImage = offScreenCanvas.snapshot(parameters, offScreenImage);
graphic.setGlobalBlendMode(BlendMode.HARD_LIGHT);
graphic.drawImage(offScreenImage, 0, 0);
graphic.setGlobalBlendMode(BlendMode.SRC_OVER);
My problem is the method snaphot() takes too much time, ~14ms, in each execution. I need to update the canvas at least at 60fps, so this consumes practically all the time I have to draw.
Is there another way to get an Image or WritableImage from a canvas? Maybe another different process?
This is another method to obtain a visual equivalent result, without reduce performance.
I have used java.awt clases, instead of JavaFX clases. The creation of a java.awt.image.BufferedImage offers the possibility to get a java.awt.Graphics2D where you can draw using other methods. The main problem here is that draw big images consumes a lot of time using this libraries, but you can create a scaled image. In my case, I have created a quarter-size BufferedImage, and I have drawn all the objects using that scale factor.
At the end of the draw process, just convert the BufferedImage, to a javafx.scene.image.Image, using:
SwingFXUtils.WritableImage toFXImage(BufferedImage bimg, WritableImage wimg);
Then print it on the main canvas using:
graphic.drawImage(Image image, 0, 0, WIDTH, HEIGHT);
To fill all the canvas with the image.
Finally, the scale factor is configurable, so if you need a detailed image, just use a higher value. For me, a 25-percent-size image is enough because I am drawing gradients. Now, it takes 1-3ms to draw the image, this is much better than before.
Hope it helps someone.

Drawing images to 4 different points

I have a quadrilateral drawn in Path2D, and I would like for there to be an image on it. More specifically, I am trying to draw an image of my choice to 4 different points on a quadrilateral. In my case, it is a parallelogram. I do not want the image to go over the paralellogram. A better way to see what I am trying to say is to see the screenshot below.
I would like the image to be transformed to fit the green area. Not clipped.
I want the image to be pinned over the green paralellogram. However. I do not want the image to go over into the blue paralellogram, or the white space foe that matter.
So far I have tried
Researching for a way to place images directly onto Path2D.Double() objects. No answer
Rotating the image to fit the paralellogram. Didnt work.
Using AffineTransform in java. Dont get it ;-;
Thanks. I am new to java so do try to be lenient?
One way is to:
create a separate BufferedImage.
Apply a transform to the new image.
Draw your image to that new image.
Use the Shape object for the green area as a clip on the main drawing area
Draw the transformed image onto the main drawing area.
It's been a while since I have done transformations. You may have to set the transformation first and then draw the image after. Transformation has to come first.
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
g2.transform(AffineTransform.getShearInstance(1.0, 0));
g2.drawImage(image, 0, 0, this);
}
Here is a simple example of how transforms work. You will have to spend some time on figuring out what values you need to make it work or if you might need to manually create a transformation matrix yourself.

Simple image rotation

I am making a game in Java. I made a planet seen from outer space and I want to make it appear like the planet is slowly rotating. But I don't know how to rotate a image. I need a simple command that rotates my image 1 degree around its own center once. Any help?
This is what I want to do:
Image
Take a look at these tutorials:
Java2D: Have Fun With Affine Transform
Coordinate Translations and Rotations: Example Code
Transforming Shapes, Text, and Images
What you are describing is not rotating an image, but changing an image to represent a 3D rotation of the object in the image.
Ideally you wouldn't be working with this as an image but rather as a 3D object with a different camera angle. Then you would simply rotate the camera around the object and display the resulting image to the user.
However if you're set on doing this as an image, then you need to create a different images representing various states of rotation of your planet and have a separate thread that would replace the displayed image with the next one in sequence, at repeated intervals. Search the web for "java image animation" - there are plenty of tutorials on how to do this.
If you want to rotate an image in 2d space, you can use something like this:
Image image = ...
Graphics2D g2d = ...; //
g2d.translate(170, 0); // If needed
g2d.rotate(1); // Rotate the image by 1 radian
//or g2d.rotate(180.0/3.14); to rotate by 1 degree
g2d.drawImage(image, 0, 0, 200, 200, observer);

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