I have a field made up of BitmapData, which I use for pixel-precise hit detection.
However, BitmapData naturally stores 2^32 (or 2^24 with no alpha?) possibilities for each pixel. I only need 2 - black or white.
But I still need to use .draw to make other objects being drawn onto that BitmapData. It doesn't need to be visible.
Extracting a pixel for hit-detection does not seem too difficult - but drawing without cycling through each pixel seems hard. Is it possible?
What would the right approach for this problem be?
If you depend on having your bitmap data to be black or white only, you can employ BitmapData.threshold() after drawing a new mask over that bitmap. To turn your existing BitmapData to black and white with a threshold of half red channel do the following:
bd.threshold(bd,bd.rect,new Point(),"<",0x00800000,0x0,0x00ff0000,true);
bd.threshold(bd,bd.rect,new Point(),">=",0x00800000,0x00ffffff,0x00ff0000,true);
The first call with turn all points that have red below 0x80 black, the second will turn all the remaining points white. Change the mask and threshold value to use green or blue channels if you want. Consider applying a properly channeled ColorTransform object to your draw calls to make the mask correctly applied to a newly drawn object.
Related
I'm trying to create a handwriting game with AS3 on Adobe Animate. I've created my board, functions(drawing, erasing, saving, printing and color pannel) so far. But i need to show a score. To do it i thought if i can calculate the percentege of intersection between drawing and a bitmap image(which is my background for now).
Is there any way to do it? Or can you at least tell me with which function should i try that? Thanks a lot.
Note: Here is 2 images from my game. You can easily understand what am i trying to explain and do.
players will try to draw correctly(drawn board)
Empty Board
just a suggestion,
lets assuming that you are recording draw data, a set of points according the frame rate that records mouse positions inside an array.
i used 8 points in my own example, the result would be like this: (6 of 8 = 75% passed)
► black line is correct path(trace btimap) ► red is client draw
we need to search whole of the points array and validate them, so a percentage will be gain easily
how to validate
each point contain x and y, to check if its placed on a black pixel (bitmap trace) we just do
if (bitmapData.getPixel(point.x, point.y) == 0x0) // 0x0 is black
getPixel returns an integer that represents an RGB pixel value from a
BitmapData object at a specific point (x, y). The getPixel() method
returns an unmultiplied pixel value. No alpha information is returned.
Improvment
this practice would be more accurate when there is really more captured points during draw, also the Trace-Bitmap must be like this (above image), not a Dashed (smoothed, styled, ...) Line, however you can use this trace bitmap in background (invisible) and only present a dashed copy of that with a colorful background (like grass and rock textures or any graphical improves) to players.
Note
also define a maximum search size if you need more speed for validating draw. this maximum will be used to ignoring some points, for example if max=5 and we have 10 points, 0,2,4,6,8 can be ignored
So I've got a field of yellow balls on the stage in rows all the way down the screen. About 200 of them. They're all movieClips linked from one ball MovieClip in the library.
I'm storing them in an Array called ballField.
I've also got a video feed on the stage (right now from webcam, but later will be whatever video I choose).
I want the video to be broken down into binary colour (black and white contrast).
Then I want to hit test all of the balls MovieClips against the color white from the video on enter frame.
Whenever a ball is 'hit' I want it to become visible. Whenever it's not hit, it will be invisible.
Essentially I want the end product to be a video created out of a field of balls (each ball would be like a binary pixel) appearing and disappearing against the white motion of the background video, (once it's working I'll hide the source) to give the illusion of a video created out of yellow balls.
This is a little over my head. I researched several options using the Bitmap data class for collision detection, but I'm not sure how to hitTest colours versus points. And I'm not sure how to hitTest bitmap data from a video to a MovieClip.
Any help is appreciated..
Hrm, one way I see to do this is for every ball, get the position of it and compare it to the pixel on the video it is supposed to match (may need to do some of your own mapping logic here). Then just look up that pixel colour to determine if the ball is visible or not. No hitTesting needed.
I am working on flash professional cs5.5 and actionscript 3. I need to use symbols of customized sizes to test the hitTestOjbect() function. However, when i convert the bitmap to a symbol, by default it goes into a rectangular size and the empty space all around is also detected as part of the symbol.
Is there any way to keep the size of the symbol customized ?
That is the nature of a bitmap. Technically, bitmaps are always rectangular. Transparent areas are just fills with alpha-0. When you convert a bitmap to a symbol, the bitmap still exists, just inside the context of the symbol.
One of the fastest ways to fix this is to use a mask inside your MovieClip. Create a plain drawing object in the exact shape of the hit area you want. Then, place that on your timeline on it's own layer. Right-click the layer with the mask, click "Mask", and then drag the bitmap's layer under the mask one. Lock both layers, and exit symbol editing.
Now your hit area will be limited to only the masked area.
EDIT: I appear to be mistaken - hitTestArea is always rectangular. See the top answer to hitTestObject Collision Not Registering Correctly.
so what I want to achieve is drawing a rectangle with either a color/fillRect or with clearRect and then copy it to the other canvas layer under the one I was drawing on. Also I want to set a background to this layer with opacity.
What I've tried is setting background with fillStyle and fillRect and it went fine. Also I could draw the rectangle with fillRect on the upper canvas which had no background and then copy the rectangle to the other one with drawImage.
Problem was when I tried to create a rectangle with clearRect and copy it. As I noticed I can only clearRect with another rectangle. But then I have to set a background to the upper canvas, which is ok, but when I copy it to the other one it gets darker and darker every time (well of course..)
So how is this possible?
When you work with alpha channel you will as you already noticed accumulate alpha channel values as long as alpha < 255. The only way to "reset" this is to start fresh so-to-speak.
Here are a couple of options to get around this -
Option 1
Don't copy anything from the draft canvas to the main canvas but store all points and shapes into a 2-dimensional array or an array consisting of the shape objects with its points, color, line width and so forth.
When you need to update the main canvas, clear both canvases and then re-render all the shapes to the main one.
Option 2
If all shapes on the main canvas is suppose to have the same opacity then use a third off-screen canvas. Draw everything to this canvas non-transparent (this last is important).
When updating main canvas clear it, set globalAlpha on it and then draw the off-screen canvas to it.
So we'll probably need some example code, because I'm not 100% sure what your trying to do... your using 2 canvas objects, drawing on the top canvas, and copying that to the bottom canvas... something like?:
ctx2.drawImage(canvas1,0,0);
then your clearing the top canvas:
ctx1.clearRect(0,0,canvas1.width,canvas1.height);
and doing your draw routine again? are you trying to get some sort of trail effect or something?
I am working on a Action Script 3.0 application , in which i ill be allowed to load the image and make them draggable. Consider i am loading the deer image and making it as draggable.
Problem with this is , if i click on the translucent area ( white space around the bitmap ), i dont want the bitmap to draggable.is there any way to draw the deer boundary region exactly without the white space around it.
You can use BitmapData methods to get each pixel color, and then, you can either :
On creation, for each pixel if it's not fully transparent (!= 0) you can draw a point of a Shape, which will be transparent, and make it dragable in place of your bitmap (as noticed in comment, it will be quite CPU consuming, so use the second method)
On click, get the click coordinate relative to the bitmap, check if the pixel is transparent and make it drag only if it's not.
In either way, that will be quite CPU consuming. You may also consider convert your bitmap to a vector image (Sprite). This will allow flash to detect real images boundaries.