Automatic cropping to a given "border" distance

Question

Dear all,
Given some hand drawings which are firmly black on white background (no greys of any kind), is it possible to somehow (in CS5 for Mac) to crop an image in such a fashion that a specified amount of whitespace is left around the drawings? I.e., determine a 'bounding box' for the drawing and then enlarge it by so much in either direction, then crop?
Thanks,
K

Answer 1

Karljürgen wrote:
1. Trim doesn't seem to work predictably, i.e. sometimes it trims, sometimes it doesn't (I've even had it cut into the drawing). I shouldn't be the fault of pixel colour, because the final images were constructed using a layer filled with white and a mask filled with black for the drawings. I can't imagine what the problem is.
Perhaps you do not understand how Trim works it may not be the tool you should be using.  I also do not understand your discription of your Photoshop document construction please give us more details. Perhaps a screen captire or an example PSD file.  The following in from Photoshop Help.
Crop an image using the Trim command
The Trim command crops an image by removing unwanted image data in different ways than the Crop command. You can crop an image by trimming surrounding transparent pixels, or background pixels of the color you specify.
Choose Image > Trim.
In the Trim dialog box, select an option:
Transparent Pixels to trim away transparency at the edges of the image, leaving the smallest image containing nontransparent pixels.
Top Left Pixel Color to remove an area the color of the upper-left pixel from the image.
Bottom Right Pixel Color to remove an area the color of the lower right pixel from the image.
Select one or more areas of the image to trim away: Top, Bottom, Left, or Right.
2. I have several hundred drawings, and they vary in size. Canvas size expects an absolute input, which I can't predict in advance, and having to compute it manually is tedious and error prone. What I need is to add a relative amount. Better yet, trim within x pixels (or whatever) of the drawing....
No Canvas size has options so added canvas can be relative to the curremt camvas size and the amount of canvas can be relative to it DPI resolution or in absolute pixel size. Where the canvas is added can also be controlled by moving the anchor point.  You wrote your document vary in size.  Even if you have a mixture of Web size images and Print size images you can create an action to add a border relative to an image's size.  Adding a little script would be helpful for dealing with size. I'll explain your images have some size you have no idea about size in an action however you can still deal with it.  An image size is determined by the number of pixels and its DPI resolution.  When it come to Web Images DPI resolution is not important Pixel size is For Displays only use their DPI and display pixels at their DPI resolition Web images are sized to fit within some  display size like 800x600 pixels.
The best way to deal with Image size in an action is to first save its current DPI resolution, then scale the image to a known width or height, make your changes based on the now known syze, then restore the image to its original DPI scale.   An Action can not save and restore and images DPI on its own it needs a little Photoshop scripting to do that.  I'll give you that.  So to add a border the will be approate for an image's size is easy
Setp 1 Script Save and Restore DPI Resolition
Step 2 Scale image to 8" wide.  Image Size Resample NOT check, Set width to 8" Click OK. All the does is change the DPI
Step 3 Add 1" border and all sides. Canvas size check Relative, set both width and height to 2", leave anchor point centered and click OK.  Add some number of pixels on all sides based on DPI.
Step 4 Script Save and Restore DPI Resolition. 
SaveAndRestoreResolution.jsx
/* ======================================================================================
// 2009  John J. McAssey (JJMack)  http://www.mouseprints.net/
// This script is supplied as is. It is provided as freeware.
// The author accepts no liability for any problems arising from its use.
// This script is designed to be used by a Photoshop Action twice
// A good pratice to use when creating an actions that use this scipt is for the action
// not to do a save or play some other action between its two useages of this Script.
// The first time this script is used by an action the documents current resolution
// and ruler units are saved into the document's meta-data Info Instructions field.
// The second time this script used by the action the script retreives what was
// saved in the meta-data during the first usage, resolution and ruler units.
// The document is resized to the saved resolution,
// Photoshop's ruler units are set to saved units
// and the saved data is removed from the document's meta-data Info Instructions field.
// ===================================================================================== */
<javascriptresource>
<about>$$$/JavaScripts/SaveAndRestoreResolution/About=JJMack's SaveAndRestoreResolution.^r^rCopyright 2009 Mouseprints.^r^rRun twice script utility for action.^rNOTE:Don't play other actions between runs!^r^rFirst Run records Photoshop's preferences Units and documents DPI resolution.^rSecond Run restores the recorded setting and removes the recording.</about>
<category>JJMack's Action Run Twice Utility</category>
</javascriptresource>
if (app.documents.length > 0) {
          if (app.activeDocument.info.instructions.indexOf("<Resolution>") == -1 ){ // no footprint fisrt useage
                    //alert("first");
                    // Retreive Document information for Foot Print
                var units = app.preferences.rulerUnits;
                    app.preferences.rulerUnits = Units.PIXELS;          // set ruler units to PIXELS
                var typeunits = app.preferences.typeUnits;
                    var res = app.activeDocument.resolution;
                    // put footprint in metadata info instructions
                    app.activeDocument.info.instructions = app.activeDocument.info.instructions + "<Units>" + units + "</Units>"  + "<Tunits>" + typeunits + "</Tunits>" + "<Resolution>" + res + "</Resolution>";
                    //alert( "Saved ="  + "<Units>" + units + "</Units>" + "<Tunits>" + typeunits + "</Tunits>" + "<Resolution>" + res + "</Resolution>" );
                    app.preferences.rulerUnits = units;                    // restore ruler units
          else {
                    //alert("second");
                    // Retreive saved information
                    unitsOffset = app.activeDocument.info.instructions.indexOf("<Units>") + "<Units>".length;
                    unitsLength = app.activeDocument.info.instructions.indexOf("</Units>") -unitsOffset;
                    savedUnits = app.activeDocument.info.instructions.substr(unitsOffset, unitsLength);
                    tunitsOffset = app.activeDocument.info.instructions.indexOf("<Tunits>") + "<Tunits>".length;
                    tunitsLength = app.activeDocument.info.instructions.indexOf("</Tunits>") -tunitsOffset;
                    savedTunits = app.activeDocument.info.instructions.substr(tunitsOffset, tunitsLength);
                    resOffset = app.activeDocument.info.instructions.indexOf("<Resolution>") + "<Resolution>".length;
                    resLength = app.activeDocument.info.instructions.indexOf("</Resolution>") + -resOffset;
                    savedResolution = app.activeDocument.info.instructions.substr(resOffset, resLength);
                    //alert("Resolution = " + savedResolution + " Units = " + savedUnits );
                    // Restore resolution
                    app.preferences.rulerUnits = Units.PIXELS;
                    activeDocument.resizeImage(null, null, savedResolution, ResampleMethod.NONE);
                    // Restore ruler units
                    // I get a message Enumerated value expected if I try to use var savedUnits app.preferences.rulerUnits = savedUnits;
                    // perhaps if I knew Javascript I would not need to use the following if else if .....
                    if ( savedUnits == "Units.INCHES" ){ app.preferences.rulerUnits = Units.INCHES;}
                    else if ( savedUnits == "Units.CM" ){ app.preferences.rulerUnits = Units.CM;}
                    else if ( savedUnits == "Units.PERCENT" ){ app.preferences.rulerUnits = Units.PERCENT;}
                    else if ( savedUnits == "Units.MM" ){ app.preferences.rulerUnits = Units.MM;}
                    else if ( savedUnits == "Units.PIXELS" ){ app.preferences.rulerUnits = Units.PIXELS;}
                    else if ( savedUnits == "Units.POINTS" ){ app.preferences.rulerUnits = Units.POINTS;}
                    else if ( savedUnits == "Units.PICAS" ){ app.preferences.rulerUnits = Units.PICAS;}
                    // Restore Type units
                    if ( savedTunits == "TypeUnits.PIXELS" ){ app.preferences.typeUnits = TypeUnits.PIXELS;}
                    else if ( savedTunits == "TypeUnits.POINTS" ){ app.preferences.typeUnits = TypeUnits.POINTS;}
                    else if ( savedTunits == "TypeUnits.MM" ){ app.preferences.typeUnits = TypeUnits.MM;}
                    // Remove footprint from metadata info instructions
                    before = app.activeDocument.info.instructions.substr(0,app.activeDocument.info.instructions.indexO f("<Units>"));
                    afterOffset = app.activeDocument.info.instructions.indexOf("</Resolution>") + "</Resolution>".length;
                    after = app.activeDocument.info.instructions.substr(afterOffset, app.activeDocument.info.instructions.length - afterOffset);
                    //alert ("before = " + before + " after = " + after);
                    app.activeDocument.info.instructions = before + after;
else { alert("You must have at least one open document to run this script!"); }