Pixel Calculator Activities - Location

Location, Location, Location...

To do this activity, the entire image must fit on your screen.

	Zoom out until your image fits completely in the Pixel Calculator window.

Look at the bottom left hand corner of the screen while you do this:

	Move your mouse around the Pixel Calculator window.

Did you notice something changing while you were moving the mouse?

What was it?

The picture position is also known as the coordinates of a pixel. The coordinates are shown as a pair of numbers like (45, 90), where 45 is the X-coordinate and 90 is the Y-coordinate.

Which directions do you move your mouse to change the X- coordinate?
up and down left and right

Which directions do you move your mouse to change the Y- coordinate?
up and down left and right

Which direction do you move your mouse to make the X- coordinate get SMALLER?
up down left right

Which direction do you move your mouse to make the Y- coordinate get BIGGER?
up down left right

What corner of the picture has the coordinates (0, 0)?

What corner of the picture has the largest coordinates? (Where the X and Y coordinates are the biggest)

Zooming into a picture position

Now you're going to learn how to zoom in to a certain coordinate or picture position. This will be really important in the activities that will follow.

	Load the image mountain.bmp by selecting File then Get Image
	Select mountain.bmp and press the OK button.
	Click on the Zooming tool to make sure its selected.
	Bring the mouse over the picture.

Now,

	Move your mouse around the Pixel Calculator window until the 
	Picture Position is NEAR (57, 74).

NEAR means the coordinates could be something like (50, 80) or (62, 71) or (57, 81). You don't have to find the exact picture position... yet...

	Zoom in by clicking with the left mouse button on the picture at that coordinate.

Zooming in may change the coordinates of your mouse, so:

	Move your mouse around the Pixel Calculator window until the 
	Picture Position is NEAR (57, 74) again.

Keep Moving and Zooming In until you see the gray values on the screen.

	NOW move your mouse until the Picture Position is EXACTLY (57, 74). 

What is the gray value of the pixel at coordinate (57, 74)?

Now let's try again with another coordinate.

	Zoom out all the way.
	Zoom in to the coordinate (387, 182)

What is the gray value of the pixel at coordinate (387, 182)?

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