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## Re: Creating picture X*Y pixel by pixel

 From: Martin Weiser Subject: Re: Creating picture X*Y pixel by pixel Date: Mon, 09 Aug 2010 20:32:01 +0200 User-agent: Internet Messaging Program (IMP) H3 (4.3.7)

```Cituji ZWD <address@hidden>:

```
```
Hello,

I want to create a picture e.g. 640x480 and want to be able to change the
color of each pixel.
So I want to create a picture pixel by pixel(and being able to say pixel on
235x198 has the color grey) and save it as a .jpg

Im a beginner in octave so any help would be great

Thanks
ZWD
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```Hello.
```
In octave, images are just matrices. Colour images are just 3 matrices (one for red, one for green, one for blue) bundled together (superimposed) into an 3D array.
```So, create your matrices, eg. like this:
# prepare them
red=zeros(2,2)
green=zeros(2,2)
blue=zeros(2,2)

#"colour" pixels in them (0-255)

#red  matrix
red(1,1)=100

#green
green(1,2)=150

#blue one
blue(2,2)=200

# bundle them together
fig=cat(3,red,green,blue)

# if you want to see that figure
image(fig)

# if you want to save it as jpeg
imwrite(fig, "some_image_name.jpg")

Simple, is not it?
```
If you need just a monochromatic (eg. white-gray-black) figure, you need just a single matrix instead of 3D array.
```
So, I hope this helps.
Martin

```