Set negative coordinates for an image in C#

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I have values of x and y coordinates in my database. On the button click event, I want to display a small dot on the image for those coordinates. e.g. The values that I have for x and y coordinates are like this:

HTML

XLoc    YLoc
0.78    -3.22
1.6     -5.02
1.29    -5.71
1       -2.26
0.6     -2.11

and so on....

What I have tried:

C#

private void btnSetCoordinates_Click(object sender, EventArgs e)
      {
          try
          {
              Bitmap PicBox1 = new Bitmap(picImage.Image);

              ((Bitmap)picImage.Image).SetPixel(txtXloc.Text, txtYLoc.Text, Color.Black);
              picImage.Refresh();

          }
          catch (Exception ex)
          {
              MessageBox.Show(ex.Message);
              throw;
          }

      }

When I try any negative value to set pixel on image, it throws an error. Can anyone please help me?

Posted 16-Jan-18 5:19am

webmail123

Updated 16-Jan-18 6:07am

v2

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F-ES Sitecore 16-Jan-18 11:36am

What do you want to happen when someone sets a pixel at a negative point?

webmail123 16-Jan-18 11:58am

I didn't get you question.
I want to show the pixel on the given x and y coordinates. As of now I am getting error saying 'Parameter must be positive.'

F-ES Sitecore 16-Jan-18 12:04pm

If an image is 100 pixels by 100 pixels then (0,0) is the upper left corner, (100, 0) the upper right, (0,100) the lower left and (100,100) the lower right, so where is -10, -10?

webmail123 16-Jan-18 13:24pm

So that's where I need help with. I need to convert those coordinates into a actual coordinates which are compatible with 100px by 100px image.(its just an example)

F-ES Sitecore 17-Jan-18 4:16am

You still haven't answered the question...on a 100x100 image where will -10,-10 appear? Until you know the answer to that question you can't write any code. You have to fully understand a problem before you can write code to solve it, you have to know the inputs and the outputs, so if the input is -10,-10 what is the output?

webmail123 18-Jan-18 8:51am

I need to convert those coordinates into pixels so that I can use it.
This is the scenario:

Basically I have a laboratory layout and that layout has coordinates like this:

- top right corner of laboratory is considered as origin (0,0)
- bottom right corner is considered as (-1, -8.6)
- top left corner is considered as (4.2 , 0)
- bottom left corner is considered as (4.2, -8.6)
- definitely midpoints are (-1, -4.3) and (4.2, -4.3)

Now if any items coordinates are (0.78, -3.22) then I want to show a dot on the image to display location of that item. So, now I have to convert (0.78 , -3.22) coordinates into standard pixel so that I can use that pixel value to display it on image. I need help for convert these coordinates into pixel.
Did you get my idea??

F-ES Sitecore 18-Jan-18 9:24am

Those points don't make mathematical sense, the coords don't seem to be describing a square as there is no coord in common between top right and bottom right. So it looks like you're trying to map a point inside a polygon using arbitrary values that we don't really understand. It's more of a maths problem than a programming one.

1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Answer 1 · 2018-01-16T06:06:00

Solution 1

Unfortunately the SetPixel documentation doesn't help. Anyway the GetPixel one[^] does:

ArgumentOutOfRangeException	

x is less than 0, or greater than or equal to Width.

-or-

y is less than 0, or greater than or equal to Height.

Basically you cannot address negative coordinates. However you may transform your coordinates in order to fit the Bitmap box.

Posted 16-Jan-18 6:06am

CPallini

Updated 16-Jan-18 6:08am

v3

Comments

webmail123 16-Jan-18 13:40pm

Thanks for the answer. And I think the same. To transform coordinates in order to fit in bitmap box. Is there any inbuilt function for it?

Basically I have a laboratory layout and that layout has coordinates like this:

- top right corner of laboratory is considered as origin (0,0)
- bottom right corner is considered as (-1, -8.6)
- top left corner is considered as (4.2 , 0)
- bottom left corner is considered as (4.2, -8.6)
- definitely midpoints are (-1, -4.3) and (4.2, -4.3)

Now if any items coordinates are (0.78, -3.22) then I want to show a dot on the image to display location of that item.
Did you get my idea??

CPallini 20-Jan-18 5:34am

Are you sure laboratory frame is not a rectangle?

Set negative coordinates for an image in C#

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Set negative coordinates for an image in C#

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