draw a line on an image

165 次查看（过去 30 天）
Fatma Gargouri
Fatma Gargouri 2011-10-3
评论： Walter Roberson 2021-1-12
Hello
I want draw a line on an image, just by giving the coordinates of the extremities.
I tryed the function line(...) but it didn't give me the right result

请先登录，再回答此问题。

采纳的回答

Fangjun Jiang
Fangjun Jiang 2011-10-3
Pay attention of the syntax of line().
line([x1,x2],[y1,y2]), not line([x1,y1],[x2,y2]);
figure(1);line([0 1],[0 1]); will show a line
figure(2);line([0 0],[1 1]); won't show a line
  6 个评论
显示 4更早的评论
Amber Elferink
Amber Elferink 2021-1-11
you have to do hold off at the end again (for next viewers)
Walter Roberson
Walter Roberson 2021-1-12
I suspect Sumit either wanted to know about getframe() https://www.mathworks.com/help/matlab/ref/getframe.html or else wanted to know how to draw a line directly into an array with the intent to save the array as an image but without having to display on the screen.
The easiest way to draw a line directly into an array is to use Computer Vision Toolbox insertShape()

请先登录，再进行评论。

更多回答（1 个）

David Young
David Young 2011-10-3
Perhaps your problem is that figure coordinates and array indices have different conventions. So, for example
imshow(im)
line([50 100], [30 30])
draws a line from im(30, 50) to im(30, 100).
Arrays are indexed by (ROW,COLUMN). Positions in a figure are addressed by (X,Y). When you display an array as an image, using the usual conventions, ROW corresponds to Y and COLUMN corresponds to X.
  12 个评论
显示 10更早的评论
Somsubhro Chaudhuri
Somsubhro Chaudhuri 2017-8-16
编辑：Somsubhro Chaudhuri 2017-8-16
Thank you @Image Analyst. I managed doing that now. I now have a binary image with a line between two points (attached). Could you please suggest a way to only change the area right below the line to black?
I was thinking of defining the equation of the line, and then running a for loop to cover these pixels, but I want to enquire about a shorter way of doing this as I'll have to run this code for a very large number of images.
Thank you! Regards, Somsubhro
Image Analyst
Image Analyst 2017-8-16
You could take the endpoints of the line, then add on the bottom of the image coordinates, then call poly2mask() to get a binary image mask. Then use that to erase the image in that quadrilateral.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Image Arithmetic 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by