Hi I am new to prolog and I need to write a function called rect_area(Width, Height, Area) that can calculate the area of a rectangle, e.g.:
?- rect_area(2, 3, A).
A = 6.
Here is my try :
rect_area(Width, Height, Area):-
read(Width), read(Height),
Area is Width * Height, write(Area),nl.
But it doesn't work. I run it and In the listener I input
?- rect_area(2, 3, A).
no is returned.
I don't know why it is like this. How to fix it?
If you are supplying Width and Height, you don't need to read them. And you might not need to print Area; it will get bound to the value and reported when rect_area finishes.
Related
For example there is an image using canvas with a rectangle in World Space. In doing so the camera/device can look around freely with the image placed into the "real" world. I wonder if there is a way to limit that "movement", spanning left to right, top to bottom but the device/camera view is limited at a certain point. Even if users turn the device/camera 360degrees, the view is stuck at a certain point. Say if the user pans left the camera/device stops at rotationY: 9, If right then stops at rotationY :-15, rotationX is stuck at 0.
I saw there's a BoundBox in the documentation but not sure what that is. There's a DeviceMotionModule but no idea how to use it. I don't know what the script example given is suppose to do.
Look into using DeviceMotion. https://sparkar.com/ar-studio/learn/documentation/reference/classes/devicemotionmodule
The script example rotates the 3d plane according to the rotation of the phone.
You will have to do some maths to position your objects according to rules and signal you get from DeviceMotion.
Using the reactive module you can access the "Clamp" method which is actually made to restrict values between two bounds. I recently found this out because I had a similar problem. From this page
clamp(x: ScalarSignal, min: ScalarSignal, max: ScalarSignal): ScalarSignal
Returns a signal with the value that is the value of the given x signal constrained to lie between the values of the given min and max signals.
Note: The behavior is undefined if min is greater than max.
I wonder know how to get the width of my string in pixels
BitmapFont API < 1.5.6
To mesure the width of a String you use your Font and get the bounds of the String, you are going to draw.
BitmapFont.getBounds(String str).width
BitmapFont API
You can get the height to for the right offset for drawing too. Just replace width with height.
In addition for multiline texts use getMultiLineBounds(someString).width to get the bounds.
BitmapFont API >= 1.5.6
The BitmapFont API changed in 1.5.7 so there is a different way to get the bounds now:
BitmapFont.TextBounds and getBounds are done. Instead, give the string to GlyphLayout and get the bounds using its width and height fields. You can then draw the text by passing the same GlyphLayout to BitmapFont, which means the glyphs don’t have to be laid out twice like they used to.
Source (Web archive)
Example:
GlyphLayout layout = new GlyphLayout(); //dont do this every frame! Store it as member
layout.setText("meow");
float width = layout.width;// contains the width of the current set text
float height = layout.height; // contains the height of the current set text
According to #Nates answer: https://stackoverflow.com/a/20759876/619673 calling method
BitmapFont.getBounds(String str).width
not always returns proper width! Especially when you are reusing font.
If you want draw text for example in the center of part of view port, you can avoid this problem by using another method
BitmapFont.drawWrapped(...)
Example code:
font.drawWrapped(spriteBatch, "text", x_pos, y_pos, your_area_for_text, BitmapFont.HAlignment.CENTER);
If you use skins in UI it is a hassle to find out the correct font to feed into the GlyphLayout.
In this case I use a throw away instance of Label to figure everything out for me then ask the Label for the width.
Skin skin = getMySkin();
Label cellExample = new Label("888.88888", skin);
cellExample.layout();
float cellWidth = cellExample.getWidth();
Table table = new Table(skin);
table.defaults().width(cellWidth);
// fill table width cells ...
This is not the answer if you want to position the text yourself, but it is useful to make a UI layout stable and less dependent on the actual content of the cells.
My application works fine, but I have a function, what calculates a minimap based on the width of the original MC, but it doesn't work when the width is negative. So the question is basically, how can width be negative? what does it mean?
thanks
--edit:
sorry, I can't post any code, it's a 30K LOC project. The solution was to include this in another movieClip, where it worked better.
I expect your MC which width you're measuring is not on stage right now. I'm experiencing the same issue with my Sprite object, if it's not on stage its width is unreliable, while I have tried not asking for width, but asking for getBounds() instead. Try first adding it to stage, then requesting width.
I don't know your code. but i'm afraid overflow occur. MovieClip property width value is Number.
Numer of the range are as follows:
4.9406564584124654e-324 <= Number <=1.79769313486231e+308
if you've initialized a positive number to width, somewhere in the code will be occur overflow.
I'm trying to position an image on top of another image based upon the make-up of the smaller image. The smaller image is a cut-out of a larger image and I need it to be positioned exactly on the larger image to make it look like a single image, but allow for separate filters and alphas to be applied. As the images are not simple rectangles or circles, but complex satellite images, I cannot simply redraw them in code. I have quite a few images and therefore do not feel like manually finding the position of each image every and hard setting them manually in actionscript. Is there any way for me to sample a small 5-10 sq. pixel area against the larger image and set the x and y values of the smaller image if a perfect match is found? All the images are in an array and iterating through them has already been set, I just need a way to sample and match pixels. My first guess was to loop the images pixel by pixel right and down, covering the whole bitmap and moving to the next child in the array once a match was found, leaving the matched child where it was when the perfect match was found.
I hope I understood your question correctly.
There may be an option that uses copypixels to achieve what you want. You can use the bitmapdata.rect value to determine the size of the sample you want, and loop through the bigger bitmap using thet rectangle and a moving point. Let's see if I can code this out...
function findBitmapInBitmap(tinyimg:BitmapData, largeimg:BitmapData):Point {
var rect:Rectangle = tinyimg.rect;
var xbound:uint = largeimg.rect.width;
var ybound:uint = largeimg.rect.height;
var imgtest:BitmapData = new BitmapData(tinyimg.rect.width, tinyimg.rect.height);
for (var ypos:uint = 0, y <= ybound, y++) {
for (var xpos:uint = 0, x <= xbound, x++) {
imgtest.copyPixels(largeimg, rect, new Point(xpos, ypos);
if (imgtest.compare(tinyimg) == 0) return new Point(xpos, ypos);
}
}
return new Point(-1,-1); // Dummy value, indicating no match.
}
Something along those lines should work - I'm sure there's room for code elegance and possible optimization. However, it seems like something like this method would be very slow, since you'd have to check each pixel for a match.
There is a better way. Split your big image into layers, and use the blitting technique to composite them at runtime. In your case, you could create a ground texture without satellites, and then create the satellites separately, and use the copyPixels method to place them whereever you want. Google "blitting in as3" to find some good tutorials. I'm currently working on a game project that uses this technique and it's a very good method.
Good luck!
Edit: Forgot to code in a default return statement. Using this method, you'd have to return an invalid point (like (-1,-1)) and check for it outside the function. Alternatively, you could just copy your small bitmap to the big one within the function, which would be much more logical, but I don't know your requirements.
You need to find pixel sequence in the big image. BitmapData.getPixel gives you pixel value. So get first pixel from small image, find it in big image, then continue comparing until you find full match. If you have trouble to code that, feel free to ask.
For the actual comparison, there's BitmapData.compare which returns the number 0 if the BitmapData objects are equivalent.
I'm currently making a color picker (pretty standard one, pretty much the same as photoshop with less options at the moment: still in early stage). Here's the picture of the actual thing : http://i.stack.imgur.com/oEvJW.jpg
The problem is : to retrieve the color of the pixel that is under the color selector (the small one, the other is the mouse), I have this line that I thought would do it :
_currentColor = Convert.hsbToHex(new HSB(0,
((_colorSelector.x + _colorSelector.width/2)*100)/_largeur,
((_colorSelector.y + _colorSelector.height/2)*100)/_hauteur
));
Just to clarify the code, I simply use the coordinates of the selector in order to create a new HSB Color (saturation is represented on the X axis and brightness (value) on the Y axis of such a color picker). I then convert this HSB Color to Hexadecimal and assign it to a property. The hue is always set to 0 at the moment but this is irrelevant as I only work with pure red to test.
It partially does what I wanted, but the returned color values are inversed for most of the corners:
for (0,0) it's supposed to return 0xFFFFFF, but it returns 0x000000 instead
for (256, 0) it's supposed to return 0xFF0000, but it returns 0x000000 instead
for (0, 256) it's supposed to return 0x000000, but it returns 0xFFFFFF instead
for (256, 256) it's supposed to return 0x000000, but it returns 0xFF0000 instead
I tried many variations in my code, but I just can't seem to fix it properly. Any reply/suggestions are more than welcomed!
I think the error (or one of them) is using values in the range 0..256 which seems to lead to overflows, try to use 0..255 instead.
Just swap the X and Y axis and it's solved.
Assuming the registration point is centered, which seems to be the case since you're doing:
(_colorSelector.x + _colorSelector.width/2)
I think you formula should look something like this:
(_colorSelector.x + _colorSelector.width/2) / _colorSelector.width
If your registration point is at (0,0), it should be just:
(_colorSelector.x / _colorSelector.width);
The above should give you a number in the range 0...1
Also, you should invert this value for brightness (because a low y value represents a high brightness and a high y value, low brightness; so brightness decreases along the y axis, while saturation increases along the x axis). So for your y axis you should do:
1 - ((_colorSelector.y + _colorSelector.height/2) / _colorSelector.height)
(Again, assuming the registration point is centered).
If your conversion function expects percentages, then you should multiply by 100
(_colorSelector.x + _colorSelector.width/2) / _colorSelector.width * 100
(1 - ((_colorSelector.y + _colorSelector.height/2) / _colorSelector.height)) * 100
Maybe I'm missing something, though. I'm not sure where _largeur and _hauteur come from, but it looks like these are width and height. I think you should use the _colorSelector height and width, but I could be wrong.
PS: I hope you get the idea, because I haven't compiled the above code and maybe I screwed up some parenthesis or made some other dumb mistake.