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Creating a box in UI image using line renderer not working

I'm planning to create a square inside UI image using line renderer but size is too small that you need to zoom In. but if its outside the UI image its working. Please see attached imaged below
the line renderer component is attached to redkey1spawn object.
Tried derHugo code it works but somehow it overshoots in the screen

Your problem is that the LineRenderer works with coordinates in Unity Units.
A Screenspace Overlay canvas has pixel size scaling so the width and height (in Unity units) match up with the width and height (in Pixels) of the Window.
→ since you add 4 points
0, 0, 0
2, 0, 0
2, -2, 0
0, -2, 0
in worldspace it means they actually on the canvas will use e.g. 2px, -2px, 0px → very small.
You could e.g. multiply the sizes by the height or width of the image/canvas.
private void Start()
{
var lineRenderer = GetComponent<LineRenderer>();
var image = GetComponentInParent<RectTransform>();
// get the Unity worldspace coordinates of the images corners
// note: to get the scales like that ofcourse only works
// if the image is never rotated!
var worlsCorners = new Vector3[4];
image.GetWorldCorners(worlsCorners);
var imageWorldSize = new Vector2(Mathf.Abs(worlsCorners[0].x - worlsCorners[2].x), Mathf.Abs(worlsCorners[1].y - worlsCorners[3].y));
var positions = new Vector3[lineRenderer.positionCount];
var pointnum = lineRenderer.GetPositions(positions);
for (var i = 0; i < pointnum; i++)
{
positions[i] = positions[i] * imageWorldSize.x;
}
lineRenderer.SetPositions(positions);
}
Note, however, I'm actually not even sure you will see this LineRenderer since it is not a UI component I'm pretty sure the ScreenSpace Overlay will make every Image etc always render on top of it.

How do I resize sprites in a C# XNA game based on window size?

I'm making a game in C# and XNA 4.0. It uses multiple objects (such as a player character, enemies, platforms, etc.), each with their own texture and hitbox. The objects are created and drawn using code similar to the following:
class Object
{
Texture2D m_texture;
Rectangle m_hitbox;
public Object(Texture2D texture, Vector2 position)
{
m_texture = texture;
m_hitbox = new Rectangle((int)position.X, (int)position.Y, texture.Width, texture.Height);
}
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture, m_hitbox, Color.White);
}
}
Everything works properly, but I also want to allow the player to resize the game window. The main game class uses the following code to do so:
private void Update(GameTime gameTime)
{
if (playerChangedWindowSize == true)
{
graphics.PreferredBackBufferHeight = newHeight;
graphics.PreferredBackBufferWidth = newWidth;
graphics.ApplyChanges();
}
}
This will inevitably cause the positions and hitboxes of the objects to become inaccurate whenever the window size is changed. Is there an easy way for me to change the positions and hitboxes based on a new window size? If the new window width was twice as big as it was before I could probably just double the width of every object's hitbox, but I'm sure that's a terrible way of doing it.

Consider normalizing your coordinate system to view space {0...1} and only apply the window dimensions scalar at the point of rendering.
View Space to Screen Space Conversion
Pseudo code for co-ordinates:
x' = x * screenResX
y' = y * screenResY
Similarly for dimensions. Let's say you have a 32x32 sprite originally designed for 1920x1080 and wish to scale so that it fits the same logical space on screen (so it doesn't appear unnaturally small):
r = 32 * screenResX' / screenResY
width' = width * r
height' = height * r
Then it won't matter what resolution the user has set.
If you are concerned over performance this may impose, then you can perform the above at screen resolution change time for a one-off computation. However you should still always keep the original viewspace {0...1}.
Collision Detection
It's arguably more efficient to perform CD on screen space coordinates
Hope this helps

Create Rect at global coordinate

My scene is 2048 x 1152, and the camera never moves. When I create a rectangle with the following:
timeBarRect = new Rect(220, 185, Screen.width / 3, Screen.height / 50);
Its position changes depending on the resolution of my game, so I can't figure out how to get it to always land where I want it on the screen. To clarify, if I set the resolution to 16:9, and change the size of the preview window, the game will resize at ratios of 16:9, but the bar will move out from where it's supposed to be.
I have two related questions:
Is it possible to place the Rect at a global coordinate? Since the screen is always 2048 x 1152, if I could just place it at a certain coordinate, it'd be perfect.
Is the Rect a UI element? When it's created, I can't find it in the hierarchy. If it's a UI element, I feel like it should be created relative to a canvas/camera, but I can't figure out a way to do that either.
Update:
I am realizing now that I was unclear about what is actually being visualized. Here is that information: Once the Rect is created, I create a texture, update the size of that texture in Update() and draw it to the Rect in OnGui():
timeTexture = new Texture2D (1, 1);
timeTexture.SetPixel(0,0, Color.green);
timeTexture.Apply();
The texture size being changed:
void Update ()
{
if (time < timerMax) {
playerCanAttack = false;
time = time + (10 * Time.deltaTime);
} else {
time = timerMax;
playerCanAttack = true;
}
The actual visualization of the Rect, which is being drawn in a different spot depending on the size of the screen:
void OnGUI(){
float ratio = time / 500;
float rectWidth = ratio * Screen.width / 1.6f;
timeBarRect.width = rectWidth;
GUI.DrawTexture (timeBarRect, timeTexture);
}

I don't know that I completely understand either of the two questions I posed, but I did discover that the way to get the rect's coordinates to match the screen no matter what resolution was not using global coordinates, but using the camera's coordinates, and placing code in Update() such that the rect's coordinates were updated:
timeBarRect.x = cam.pixelWidth / timerWidth;
timeBarRect.y = cam.pixelHeight / timerHeight;

Positioning Graphics draw

I'm trying to draw some polygons and lines usinng e.Graphics.DrawPolygon (or DrawLine). But I have a little problem specifying the coordinates where to draw. I am drawing onto a PictureBox using its Paint event. The elements draw correctly relatively to each other (creating the required final picture), but seem always to draw in the upper-left corner of the PictureBox. When creating the points to draw, when I just try to multiply the coordinates, it draws it at the same place but bigger (size is multiplied, instead of location coordinates).
Here is my code:
//some for loop
{
//getting the coordinates
Point toAdd = new Point((int)xCoord, (int)yCoord); // creating the point from originaly a double, here i tried to multiply..
tmpPoints.Add(toAdd); // tmpPoints is a List<Point>
}
points.Add(tmpPoints.ToArray()); //List<Point[]>
drawBuffer = points; //saving to a public List<Point[]>
points.Clear();
this.Invalidate();
here part of the pictureBox1_Paint method:
for (int i = 0; i < drawBuffer.Count; i++)
{
//some other stuff like deciding which color to use, not very important
Brush br = new SolidBrush(polyColor);
e.Graphics.FillPolygon(br, drawBuffer[i]);
brush.Dispose();
}
I have checked using breakpoint, the coordiinates are the same ratio (what was 100 pixels wide is still 100 pixels wide), they are at coordinates like x 3000 and y 1500, but it just draws itself in the upper-left corner. When i multiply the coordinates 3 times (see the code for the place where i multiplied), it draws at the same place but 3 times bigger (doesn't make sense after checking the coords...)
So, my question is - how do I set the location correctly, or is there any other way to do this?
Like this (I know, this is nonsense, just an example)
foreach(Polygon poly in e.Graphics)
{
poly.Location = new Point(poly.Location.X * 2, poly.Location.Y * 2);
}

When you multiply the coordinates of the points, they're scaled around the point (0, 0), the top-left corner of the canvas:
In order to scale it around its center (and I suppose you expected it to work this way), you need to calculate some kind of center of the polygon. For simplicity, it can be even an arithmetic mean of the coordinates, on X and Y axes respectively. If you already have the coordinates of the center, translate the coordinates of every point by a reversed vector made from the center coordinates (this is how it would look like if you drew it after this operation - the polygon's center is in the center of the coordinate system):
Now, do your scaling:
and move it back by the vector of polygon's center coordinates:

when you multiply
poly.Location = new Point(poly.Location.X * 2, poly.Location.Y * 2);
you are doing a stretch operation when you add
poly.Location = new Point(poly.Location.X + 50, poly.Location.Y +50); you are doing a translation operation.

If you want to shift everything without modifying the stored coords then just translate the graphics before drawing:
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
e.Graphics.TranslateTransform(100, 100); // shift the origin somehow
// ... draw the polygons as before ...
}

Drag & Drop modyfiing polygon shape by moving vertices in C#

I have to do application for tilling in C#. The tiles will have some shape and my app should be able to modify the shape. I will have a some shape - polygon, made from vertices. I will have for example field of 16 vertices, then I draw the polygon.
What I need to know how can I move with the the vertice using drag and drop. I will also have to recount other vertices in order to fit one tile to next tile, but it's just some math.
To conclude:
I have polygon defined 16 vertices in field of Vertices, I move (with mouse) with one vertice, recount the coordinates of ohter vertices and draw new polygon. My problem is moving (probably using drag & drop) with one vertice from filed of vertices.
This is what part of my previous code without drag & drop - just for idea what tools I'm using for drawing one tile:
private Bitmap canvasBitmap; //canvas for drawing
private Graphics g; // enter to graphics tool
Bitmap b = (Bitmap)Bitmap.FromFile("obr.bmp");
TextureBrush brush = new TextureBrush(b);
Pen pen = new Pen(Color.Black, 1);
hexaVertices[0] = new PointF(-40 + 40, 0 + 30);
hexaVertices[1] = new PointF(-20 + 40, 30 + 30);
hexaVertices[2] = new PointF(20 + 40, 30 + 30);
hexaVertices[3] = new PointF(40 + 40, 0 + 30);
hexaVertices[4] = new PointF(20 + 40, -30 + 30);
hexaVertices[5] = new PointF(-20 + 40, -30 + 30);
g.FillPolygon(brush, hexaVertices);
g.DrawPolygon(pen, hexaVertices);
Thx for advices.

I can only give you a rough outline for Windows Forms here. In WPF you could use Adorners and there are tutorials out there for how to do it. Here we go for a manual process in Windows Forms:
First, the array of vertices should be a member variable of the class and should be initialized only once at the start of the program.
Then, draw the polygon with the current set of vertices as you're doing right now. Also, draw some "handles" if you want, so you know that the vertices can be grabbed (this could be rectangles around the actual PointF).
Now for the magic :-) Assign the MouseDown, MouseMove and MouseUp events to the control you're using for displaying the image. Also, create a new member variable bool m_draggingVertex and another that contains the index to the vertex array of the vertex you're currently dragging.
In MouseDown:
Check whether the current mouse position is within the range of a vertext (I would assume a 5x5 rectangle around a vertex, so that is is easier to hit with the cursor). If you pressed the button on a vertex, set m_draggingVertex to true and store the index of the vertex in the other variable.
In MouseMove:
If m_draggingVertex is true, change the vertext at the index stored above to the new coordinates, recalc your positions and repaint so that the current position of the vertex is shown.
In MouseUp:
If m_draggingVertex is true, set it to false and do final work.
This is how I'd do it ...