int main()
{
const auto console = ::GetConsoleWindow();
const auto context = ::GetDC(console);
constexpr auto red = RGB(255, 0, 0);
constexpr auto yellow = RGB(255, 255, 0);
RECT rectClient, rectWindow;
GetClientRect(console, &rectClient);
GetWindowRect(console, &rectWindow);
int posx, posy;
posx = GetSystemMetrics(SM_CXSCREEN) / 2 - (rectWindow.right - rectWindow.left) / 2;
posy = GetSystemMetrics(SM_CYSCREEN) / 2 - (rectWindow.bottom - rectWindow.top) / 2;
const int radius = 150;
for (int y = -radius; y <= radius; y++)
for (int x = -radius; x <= radius; x++)
if (x * x + y * y <= radius * radius)
SetPixel(context, posx + x, posy + y, red);
}
It gives me this result img
it looks good but i saw this weird pixels at sides (up, down, right, left)
img
and this is what I want (I added some pixels at the top so it looks better)
enter image description here
Your "what I want" looks anti-aliased. So draw anti-aliased.
If the original condition is not met, but x*x + y*y <= (radius+1)*(radius+1) is met then you need a partially-shaded pixel.
Another way to do anti-aliasing is to test not the center of each pixel but the four corners (x \plusminus 0.5, y \plusminus 0.5). If more than zero but fewer than four corners are inside the circle, you need a partially-shaded pixel.
Related
I am trying to simply produce a grid of 5 rotated rectangles. But the grid will not come out centered. Can anyone help me out?
int margin = 150; //padding to sides and top/bottom
int rectH = 60; // height of rectangle
int rectW = 20; // width of rectangle
int n_rectangles = 5; // 5 rectangles to draw
size(800,800);
for (int x = margin+rectW; x <= width - margin; x += (width-2*(margin+rectW))/n_rectangles) {
for (int y = margin+rectH; y <= height - margin; y += (height-2*(margin+rectH))/n_rectangles) {
fill(255);
//now rotate matrix 45 degrees
pushMatrix();
translate(x, y);
rotate(radians(45));
// draw rectangle at x,y point
rect(0, 0, rectW, rectH);
popMatrix();
}
}
I recommend to draw single "centered" rectangles, the origin of the rectangle is (-rectW/2, -rectH/2):
rect(-rectW/2, -rectH/2, rectW, rectH);
Calculate the distance of the first rectangle center tor the last rectangle center, for row and column:
int size_x = margin * (n_rectangles-1);
int size_y = margin * (n_rectangles-1);
Translate to the center of the screen (width/2, height/2),
to the position of the upper left rectangle (-size_x/2, -size_y/2)
and finally each rectangle to its position (i*margin, j*margin):
translate(width/2 - size_x/2 + i*margin, height/2 - size_y/2 + j*margin);
See the final code:
int margin = 150; //padding to sides and top/bottom
int rectH = 60; // height of rectangle
int rectW = 20; // width of rectangle
int n_rectangles = 5; // 5 rectangles to draw
size(800,800);
int size_x = margin * (n_rectangles-1);
int size_y = margin * (n_rectangles-1);
for (int i = 0; i < n_rectangles; ++i ) {
for (int j = 0; j < n_rectangles; ++j ) {
fill(255);
pushMatrix();
translate(width/2 - size_x/2 + i*margin, height/2 -size_y/2 + j*margin);
rotate(radians(45));
rect(-rectW/2, -rectH/2, rectW, rectH);
popMatrix();
}
}
I have a problem where I have to select all squares (think pixels) that are partially within a circle (even if the circle only cuts through a small corner of the square, but not if it goes through one of the corner vertices). The radius is an integer multiple of the pixel size.
The problem is that the center of the circle is between pixels, i.e. on the corner vertices of four pixels.
I want to visit each pixel only once.
For example, I would like to select all white pixels in the following images:
R = 8 px
R = 10 px
For a circle with the center in the center of a pixel, this wouldn't be a problem, and I could use the usual form of the Bresenham algorithm:
public void checkCircle(int x0, int y0, int radius) {
int x = radius;
int y = 0;
int err = -x;
while (x > 0) {
while (err <= 0) {
y++;
err += 2 * y + 1;
}
checkVLine(x0 + x, y0 - y, y0 + y);
checkVLine(x0 - x, y0 - y, y0 + y);
x--;
err -= 2 * x + 1;
}
checkVLine(x0, y0 - radius, y0 + radius);
}
public void checkVLine(int x, int y0, int y1) {
assert(y0 <= y1);
for (int y = y0; y <= y1; y++)
checkPixel(x, y);
}
Sadly, I don't see how to adapt it to support inter-pixel circles.
For the first quadrant - cell should be marked if its left bottom corner lies inside circle, so you can rasterize with simple loops
for dy = 0 to R-1
dx = 0
sq = R * R - dy * dy
while dx * dx < sq
mark (dx, dy)
mark (dx, -dy-1)
mark (-dx-1, dy)
mark (-dx-1, -dy-1)
To fill whole horizontal lines, you can calculate max value for dx
for dy = 0 to R-1
mdx = Floor(Sqrt(R * R - dy * dy))
fill line (-mdx-1,dy)-(mdx,dy)
fill line (-mdx-1,-dy-1)-(mdx,-dy-1)
I'm using Processing to get a webcam feed from my laptop. In the top left corner, I have drawn a rectangle over the displayed feed. I'm trying to get the average color of the webcam, but only in the region contained by that rectangle.
I keep getting color (0, 0, 0), black, as the result.
Thank you all!
PS sorry if my code seems messy..I'm new at Processing and so I don't know if this might be hard to read or contain bad practices. Thank you.
import processing.video.*;
Capture webcam;
Capture cap;
PImage bg_img;
color bgColor = color(0, 0, 0);
int rMargin = 50;
int rWidth = 100;
color input = color(0, 0, 0);
color background = color(255, 255, 255);
color current;
int bgTolerance = 5;
void setup() {
size(1280,720);
// start the webcam
String[] inputs = Capture.list();
if (inputs.length == 0) {
println("Couldn't detect any webcams connected!");
exit();
}
webcam = new Capture(this, inputs[0]);
webcam.start();
}
void draw() {
if (webcam.available()) {
// read from the webcam
webcam.read();
image(webcam, 0,0);
webcam.loadPixels();
noFill();
strokeWeight(2);
stroke(255,255, 255);
rect(rMargin, rMargin, rWidth, rWidth);
int yCenter = (rWidth/2) + rMargin;
int xCenter = (rWidth/2) + rMargin;
// rectMode(CENTER);
int rectCenterIndex = (width* yCenter) + xCenter;
int r = 0, g = 0, b = 0;
//for whole image:
//for (int i=0; i<bg_img.pixels.length; i++) {
// color c = bg_img.pixels[i];
// r += c>>16&0xFF;
// g += c>>8&0xFF;
// b += c&0xFF;
//}
//r /= bg_img.pixels.length;
//g /= bg_img.pixels.length;
//b /= bg_img.pixels.length;
//CALCULATE AVG COLOR:
int i;
for(int x = 50; x <= 150; x++){
for(int y = 50; y <= 150; y++){
i = (width*y) + x;
color c = webcam.pixels[i];
r += c>>16&0xFF;
g += c>>8&0xFF;
b += c&0xFF;
}
}
r /= webcam.pixels.length;
g /= webcam.pixels.length;
b /= webcam.pixels.length;
println(r + " " + g + " " + b);
}
}
You're so close, but missing out one important aspect: the number of pixels you're sampling.
Notice in the example code that is commented out for a full image you're dividing by the full number of pixels (pixels.length).
However, in your adapted version you want to compute the average colour of only a subsection of the full image which means a smaller number of pixels.
You're only sampling an area that is 100x100 pixels meaning you need to divide by 10000 instead of webcam.pixels.length (1920x1000). That is why you get 0 as it's integer division.
This is what I mean in code:
int totalSampledPixels = rWidth * rWidth;
r /= totalSampledPixels;
g /= totalSampledPixels;
b /= totalSampledPixels;
Full tweaked sketch:
import processing.video.*;
Capture webcam;
Capture cap;
PImage bg_img;
color bgColor = color(0, 0, 0);
int rMargin = 50;
int rWidth = 100;
int rHeight = 100;
color input = color(0, 0, 0);
color background = color(255, 255, 255);
color current;
int bgTolerance = 5;
void setup() {
size(1280,720);
// start the webcam
String[] inputs = Capture.list();
if (inputs.length == 0) {
println("Couldn't detect any webcams connected!");
exit();
}
webcam = new Capture(this, inputs[0]);
webcam.start();
}
void draw() {
if (webcam.available()) {
// read from the webcam
webcam.read();
image(webcam, 0,0);
webcam.loadPixels();
noFill();
strokeWeight(2);
stroke(255,255, 255);
rect(rMargin, rMargin, rWidth, rHeight);
int yCenter = (rWidth/2) + rMargin;
int xCenter = (rWidth/2) + rMargin;
// rectMode(CENTER);
int rectCenterIndex = (width* yCenter) + xCenter;
int r = 0, g = 0, b = 0;
//for whole image:
//for (int i=0; i<bg_img.pixels.length; i++) {
// color c = bg_img.pixels[i];
// r += c>>16&0xFF;
// g += c>>8&0xFF;
// b += c&0xFF;
//}
//r /= bg_img.pixels.length;
//g /= bg_img.pixels.length;
//b /= bg_img.pixels.length;
//CALCULATE AVG COLOR:
int i;
for(int x = 0; x <= width; x++){
for(int y = 0; y <= height; y++){
if (x >= rMargin && x <= rMargin + rWidth && y >= rMargin && y <= rMargin + rHeight){
i = (width*y) + x;
color c = webcam.pixels[i];
r += c>>16&0xFF;
g += c>>8&0xFF;
b += c&0xFF;
}
}
}
//divide by just the area sampled (x >= 50 && x <= 150 && y >= 50 && y <= 150 is a 100x100 px area)
int totalSampledPixels = rWidth * rHeight;
r /= totalSampledPixels;
g /= totalSampledPixels;
b /= totalSampledPixels;
fill(r,g,b);
rect(rMargin + rWidth, rMargin, rWidth, rHeight);
println(r + " " + g + " " + b);
}
}
Bare in mind this is averaging in the RGB colour space which is not the same as perceptual colour space. For example, if you average red and yellow you'd expect orange, but in RGB, a bit of red and green makes yellow.
Hopefully the RGB average is good enough for what you need, otherwise you may need to convert from RGB to CIE XYZ colour space then to Lab colour space to compute the perceptual average (then convert back to XYZ and RGB to display on screen). If that is something you're interested in trying, you can find an older answer demonstrating this in openFrameworks (which you'll notice can be similar to Processing in simple scenarios).
I am working on a game that rotates an object on the z axis. I need to limit the total rotation to 80 degrees. I tried the following code, but it doesn't work. minAngle = -40.0f and maxAngle = 40.0f
Vector3 pos = transform.position;
pos.z = Mathf.Clamp(pos.z, minAngle, maxAngle);
transform.position = pos;
The code you posted clamps the z position. What you want is to use transform.rotation
void ClampRotation(float minAngle, float maxAngle, float clampAroundAngle = 0)
{
//clampAroundAngle is the angle you want the clamp to originate from
//For example a value of 90, with a min=-45 and max=45, will let the angle go 45 degrees away from 90
//Adjust to make 0 be right side up
clampAroundAngle += 180;
//Get the angle of the z axis and rotate it up side down
float z = transform.rotation.eulerAngles.z - clampAroundAngle;
z = WrapAngle(z);
//Move range to [-180, 180]
z -= 180;
//Clamp to desired range
z = Mathf.Clamp(z, minAngle, maxAngle);
//Move range back to [0, 360]
z += 180;
//Set the angle back to the transform and rotate it back to right side up
transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, transform.rotation.eulerAngles.y, z + clampAroundAngle);
}
//Make sure angle is within 0,360 range
float WrapAngle(float angle)
{
//If its negative rotate until its positive
while (angle < 0)
angle += 360;
//If its to positive rotate until within range
return Mathf.Repeat(angle, 360);
}
Here's a static version of the nice solution by Imapler that, instead of changing the angle itself, it returns the campled angle, so it can be used with any axis.
public static float ClampAngle(
float currentValue,
float minAngle,
float maxAngle,
float clampAroundAngle = 0
) {
return Mathf.Clamp(
WrapAngle(currentValue - (clampAroundAngle + 180)) - 180,
minAngle,
maxAngle
) + 360 + clampAroundAngle;
}
public static float WrapAngle(float angle)
{
while (angle < 0) {
angle += 360;
}
return Mathf.Repeat(angle, 360);
}
Or if you don't expect to use the WrapAngle method, here's an all-in-one version:
public static float ClampAngle(
float currentValue,
float minAngle,
float maxAngle,
float clampAroundAngle = 0
) {
float angle = currentValue - (clampAroundAngle + 180);
while (angle < 0) {
angle += 360;
}
angle = Mathf.Repeat(angle, 360);
return Mathf.Clamp(
angle - 180,
minAngle,
maxAngle
) + 360 + clampAroundAngle;
}
So now you can do:
transform.localEulerAngles.x = YourMathf.ClampAngle(
transform.localEulerAngles.x,
minX,
maxX
);
I have a bezier curve defined by start point, end point and 2 control points (parameters of this: http://www.w3schools.com/tags/canvas_beziercurveto.asp).
First, I need to calculate width and height of this curve. If I make rectangle around a curve, its width and height is what I need.
Then I need to start point (x,y of left top corner) of this rectangle.
How can I calculate that ? Thanks.
For true bounds, you need to compute the extremities of the curve's component functions, then plug those into the bezier function for the (x,y) coordinates for each extremity. I cover this over at http://pomax.github.io/bezierinfo/#extremities, which also explains how to do most of the steps required to get there in the text leading up to the extremities section. paragraphs 11 and 12/13 then cover bounding boxes (plain, which you're probably interested in, and tight, respectively)
I found approximate solution in some other topic (I don't remember which one) but here is simple JS function to calculate it:
function getCurveBoundary(ax, ay, bx, by, cx, cy, dx, dy) {
var tobx = bx - ax;
var toby = by - ay;
var tocx = cx - bx;
var tocy = cy - by;
var todx = dx - cx;
var tody = dy - cy;
var step = 1 / 40; // precission
var d, px, py, qx, qy, rx, ry, tx, ty, sx, sy, x, y, i, minx, miny, maxx, maxy;
function min(num1, num2) {
if (num1 > num2)
return num2;
if (num1 < num2)
return num1;
return num1;
}
function max(num1, num2) {
if (num1 > num2)
return num1;
if (num1 < num2)
return num2;
return num1;
}
for (var i = 0; i < 41; i++)
{
d = i * step;
px = ax + d * tobx;
py = ay + d * toby;
qx = bx + d * tocx;
qy = by + d * tocy;
rx = cx + d * todx;
ry = cy + d * tody;
toqx = qx - px;
toqy = qy - py;
torx = rx - qx;
tory = ry - qy;
sx = px + d * toqx;
sy = py + d * toqy;
tx = qx + d * torx;
ty = qy + d * tory;
totx = tx - sx;
toty = ty - sy;
x = sx + d * totx;
y = sy + d * toty;
if (i == 0)
{
minx = x;
miny = y;
maxx = x;
maxy = y;
}
else
{
minx = min(minx, x);
miny = min(miny, y);
maxx = max(maxx, x);
maxy = max(maxy, y);
}
}
return {x: Math.round(minx), y: Math.round(miny), width: Math.round(maxx - minx), height: Math.round(maxy - miny)};
}
If you're looking for an approximate solution, it's pretty easy to compute a solution that's always big enough to cover the curve, but might be too big.
Beziers satisfy the 'convex hull property' which means that you can take a bounding box of your control points and that will bound the curve itself.
If you're looking for something more accurate, then the simplest way is to evaluate a bunch of different points on the curve and take the bounding box of those points on the curve. You can vary the number of points you test in order to change the quality/speed tradeoff.
If you're looking for something that directly computes the exact answer then what you need is a root finder to look for extrema of the functions x(t) and y(t).