I'm trying to get four coordinates on an image which has an white rectangle with black color drawing.
I'v tried the extreme point technic from opencv
leftmost = tuple(contour[contour[:,:,0].argmin()][0])
rightmost = tuple(contour[contour[:,:,0].argmax()][0])
topmost = tuple(contour[contour[:,:,1].argmin()][0])
bottommost = tuple(contour[contour[:,:,1].argmax()][0])
but I got below image
However What I really want is the every vertex of a white rectangle.
Is there a way to get the four red points?
Related
I'm trying to use a render pass descriptor to draw two grayscale textures. I am drawing a black square first, then a light gray square after. The second square partially covers the first.
With this setup, the light gray square will always appear in front of the black square because it was drawn most recently in the render pass. However, I would like to know if there is a way to draw the black square above the light gray one based on its brightness. Since the squares only partially overlap is there a way to still have the black square appear on top simply because it has a darker pixel value?
Currently it looks something like this, where the gray square is drawn second so it appears on top.
What I would like is to be able to still draw the gray square second, but have it appear underneath based on the pixel brightness, like so:
I think MTLBlendOperationMin will do what you want: https://developer.apple.com/documentation/metal/mtlblendoperation/mtlblendoperationmin?language=objc
I have an image with a bright center but dark edges. I need to draw rectangle at a certain brightness, so that the darker areas remain outside. Or get the coordinates of this frame. Preferably using OpenCV, the programming language is not important.
The perimeter around a circle gets pixelated when scaling down the image.
The embedded circle image has a radius of 100 pixels. (The circle is white so click around the blank space, and you'll get the image.) Scaling down using SpriteKit causes the border to get very blurry and pixelated. How to scale up/down and preserve sharp borders in SpriteKit? The goal is to use a base image for a circle and create circle images of different sizes with this one base image.
// Create dot
let dot = SKSpriteNode(imageNamed: "dot50")
// Position dot
dot.position = scenePoint
// Size dot
let scale = radius / MasterDotRadius
println("Dot size and scale: \(radius) and \(scale)")
dot.setScale(scale)
dot.texture!.filteringMode = .Nearest
It seems you should use SKTextureFilteringLinear instead of SKTextureFilteringNearest:
SKTextureFilteringNearest:
Each pixel is drawn using the nearest point in the texture. This mode
is faster, but the results are often pixelated.
SKTextureFilteringLinear:
Each pixel is drawn by using a linear filter of multiple texels in the
texture. This mode produces higher quality results but may be slower.
You can use SKShapeNode which will act better while scale animation, but end result (when dot is scaled to some value) will be almost pixelated as when using SKSpriteNode and image.
In OpenCV, i know how to draw circles, but is there a way to get back all the points that makeup the circle? I hope I dont have to go through calculating contours.
Thanks
If you know how to draw the circle,
Create a black image with the same size of as that of original image
Then draw the circle on the black image with white color
Now in this black image, check the points which are white
If you are using Python API, you can do as follows :
import numpy as np
import cv2
img = np.zeros((500,500),np.uint8)
cv2.circle(img,(250,250),100,255)
points = np.transpose(np.where(img==255))
You can do similar thing to the answer implemented in python in C/C++
If you know how to draw the circle,
Create a black image with the same size of as that of original image
Then draw the circle on the black image with white color
Now instead of checking which pixels have certain value you can find a contour (represented as vector of points) of the circle's edge.
To do this you can use OpenCV's findContours function which will give you the points on the circles edge.
Actually the background doesn't have to be black and the circle white, but the background should be plain and the circle should have different color than background.
i have been trying to draw a rounded rectangle with spacing in the border, but i cant seem to find a way to do this using the Canvas.RoundRect function, and i am not that good in maths to draw the edges myself, i can draw a rectangle with spacing using the Canvas.MoveTo and Canvas.LineTo functions, but i dont know how to make the edges rounded. Currently what i am doing is i make yellow rectangle at the place where i want to make the spacing in the border but the problem is when i am printing i have to directly draw on printer canvas and i have to draw on a transparent sheet, so a background color will cause problems. Anyone who can help me build a custom drawing routine or tell me how can i erase that area and still print on a transparent paper without any background color. The yellow background color is just for a preview, when i am drawing to a printer canvas the background is transparent.
See the image to know what i mean by spacing in the border line.
Thanks
You can exclude the gap by manipulating the clipping region of the current device context. Assuming that L, R, T and B are the coordinates of your yellow rectangle to make the gap, use the following code:
ExcludeClipRect(Canvas.Handle, L, T, R, B); // exclude the gap
Canvas.RoundRect(<whatever you already do here>);
SelectClipRgn(Canvas.Handle, 0); // reset the clipping region
You can draw your partial rounded rectangle yourself. Use MoveTo and LineTo for the straight portions, and use Arc for the corners.
The Arc function draws a portion of an ellipse. The first two pairs of coordinates to the function indicate the bounds of the ellipse. If you want the corners of your rectangle to be circular, then the ellipse is a circle, and X2 - X1 will equal Y2 - Y1. The second two pairs of coordinates indicate the starting and ending points on the circle; they'll be the same points you pass to MoveTo and LineTo for the straight portions. The arc is drawn counter-clockwise.