Unselected Rectangle Keeper

MJW · November 17, 2016

This is a plugin I wrote a while ago, which I posted to a thread titled crop black and white images down to the smallest rectangular size that contains the black part. Apparently inspired by the thread's title, I chose the rather awkward name Unselected Rectangle Keeper. It's in the Selection submenu. It has no user interface.

This is the plugin: UnselectedRectangleKeeper.zip

The icon:

What it does sounds kind of strange, but is useful for cropping images to the smallest region that doesn't match the surrounding color.

If you have a rectangular selection which contains a non-selected region, it erases everything in the selection that's outside the bounding rectangle of the non-selected region:

To crop to the smallest rectangle containing something not matching the color of the background:

Use the Magic Wand with a low tolerance to select the outside color.

Run Unselected Rectangle Keeper.

Deselect.

Use the Magic Wand to select the transparent region.

Invert the selection.

Crop to the selection.

Example:

Before (white region is selected).

UnselectedRectangeKeeperBefore_zpsdihyid

After.

UnselectedRectangeKeeperAfter_zpsanywvxn

The code:

Spoiler


// Author: MJW
// Name: Unselected Rectangle Keeper
// Title: Unselected Rectangle Keeper
// Submenu: Selection
// Desc: Erase the area outside the bounding rectangle of the unselected interior.
// Keywords: erase unselected region rectangle
#region UICode
#endregion

private volatile bool firstTime = true;
private object myLock = new object();

int left, right, top, bottom;
void Render(Surface dst, Surface src, Rectangle rect)
{
    PdnRegion selectionRegion = EnvironmentParameters.GetSelection(src.Bounds);
    Rectangle selection = selectionRegion.GetBoundsInt();
    ColorBgra CurrentPixel;

    if (firstTime) lock (myLock)
    {
        if (firstTime)
        {
            int l = int.MaxValue, r = -1, t = int.MaxValue, b = -1;
            for (int y = selection.Top; y < selection.Bottom; y++)
            {
                for (int x = selection.Left; x < selection.Right; x++)
                {
                    if (!selectionRegion.IsVisible(x, y))
                    {
                        if (x < l)
                            l = x;
                        if (x > r)
                            r = x;
                        if (t == int.MaxValue)
                            t = y;
                        b = y;
                    }
                }
            }

            right = r; left = l; top = t; bottom = b;
            firstTime = false;
        }
    }

    // Erase everything outside the bounding rectangle for the unselected region.
    for (int y = rect.Top; y < rect.Bottom; y++)
    {
        for (int x = rect.Left; x < rect.Right; x++)
        {
            ColorBgra pixel;
            if ((y < top) || (y > bottom) || (x < left) || (x > right))
                pixel = ColorBgra.Transparent;
            else
                pixel = src[x, y];
            dst[x, y] = pixel;
        }
    }
}

EDIT: Added link to plugin (which I completely forgot to do). Thanks for the reminder, lynxster4!

EDIT 2: Added the source code. (Using the "firstTime" flag is no longer necessary. CodeLab now supports PreRender.)

lynxster4 · November 17, 2016

@MJW....maybe you should post the zip file above, so everyone doesn't have to go the link you provided?

They can go to the link for more information.

Maximilian · February 18, 2017

I've just stumbled upon this plugin and thought I'd provide a compilation for PdN 3.5.11 should anyone need it. Thanks for the code and icon, MJW!

Unselected Rectangle Keeper for PdN 3.5.11.zip