How to convert matrix indexes to cartesian coordinates

30 次查看（过去 30 天）
Tchilabalo
Tchilabalo 2019-8-24
评论： Tchilabalo 2019-8-25
Capture.JPG
Given a matrix a shown above, i want to convert the cell indexes into cartesian coordinates. I am trying to figure out what these indexes represent: is it the center of the cell? or the left corner of the cell? Thanks.
  2 个评论
TADA
TADA 2019-8-24
It's both, it's neither... If this is for visualization, I'd prefer the center of the cell But generally its up to you to decide

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2019-8-24
Matrices are just arrays of values and there is no inherent Cartesian coordinates associated with them. They have rows and columns, not x and y.
If you use imshow() or image() or imagesc() to display an image, then you have the option to control how rows and columns map into data units. The default is a 1:1 mapping. The default for all three functions is that X=1 Y=1 will correspond to the center of the bottom left pixel and that X=columns Y=rows maps to the center of the upper-right pixel. Because the center are being referred to, the image would cover from (1/2,1/2) to (columns+1/2, rows+1/2)
There are other possibilities, such as georefferencing through the Mapping Toolbox, which provides some flexibility as to what coordinates mean, possibly including nonlinear projections. In such cases the person who created the dataset should have documented the transformation.
It is common for people to get confused with images and think that there should be a way to convert pixels into real world coordinates. Sometimes there are ways, but unless you are using a calibrated device such as MRI or confocal microscope, even if image has the appropriate headers then the headers are typically pretty wrong.

更多回答（1 个）

David Hill
David Hill 2019-8-24
n=3;%nxn matrix
a=1:n^2;
x=floor((a-.1)/n)+1;
y=mod(a,n);
y(find(y==0))=n;
plot(x,y,'LineStyle','none','Marker','o',"Color",'b');

类别

在 Help Center 和 File Exchange 中查找有关 Modify Image Colors 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