Support slicewise assignment.

[gvwilson]

The following code doesn't work:

grid = ImageGrid(4, 4)
grid[0:2, 0:2] = grid[1:3, 1:3]

We would like it to for teaching purposes. We would also like:

grid[0:2, 0:2].red = 128

and similar.

[jiffyclub]

First item fixed in #23. Second shouldn't be too hard to add either with a property setter. The one thing I worry about there is that grid[:2, :2].red, etc. will be odd birds in the sense that they will only exist as setters, trying to get those attributes will raise exceptions.

[gvwilson]

On 2013-08-01 3:59 PM, Matt Davis wrote:

First item fixed in #23
#23. Second
shouldn't be too hard to add either with a property setter. The one
thing I worry about there is that |grid[:2, :2].red|, etc. will be odd
birds in the sense that they will only exist as setters, trying to
/get/ those attributes will raise exceptions.

Why will they only exist as setters? I think it makes sense to say:

grid[:, :].red = other_grid[:, :].green

or

grid[:, :].red = grid[:, :].red / 2

[jiffyclub]

Hmm, your first example maybe, if we think of grid[:, :].green as a nested list of integers.

But that won't work with your second example unless we bring numpy into the picture.

[gvwilson]

On 2013-08-01 5:44 PM, Matt Davis wrote:

Hmm, your first example maybe, if we think of |grid[:, :].green| as a
nested list of integers.

But that won't work with your second example unless we bring numpy
into the picture.

Let's ticket it, and I'll try to find a volunteer to work on it? We had
a few respond to our call on Twitter...
Thx,
G

[jiffyclub]

And I should have said that bringing numpy into the picture is not an option. I'm keeping this dependency free.

I've mentally sketched out how to implement this, I think I should be able to get it done in an hour here sometime.

[jiffyclub]

Actually, grid.red could be a new BlockGrid with the red and green channels set to zero... (Or we could add gray-scale support). We'd have to implement __div__ on BlockGrid to support the math, but that could be done. That has some interesting parallels to PIL and making RGB images by merging three layers.

[jiffyclub]

Thinking about this a bit more going the route of monochrome grids seems like the thing to do. If we just use nested lists then indexing won't match for ImageGrid.

[jiffyclub]

Okay:

• monochrome grids: Monochrome grids #24
• grid color properties: Grid color properties #25

If I get a chance I'd like to do these myself, but no promises on timeliness.

[jiffyclub]

Grid to grid assignment added in #23.