[New Feature] Autocrop

index.js

@@ -729,6 +729,92 @@ Jimp.prototype.crop = function (x, y, w, h, cb) {
     else return this;
 };
 
+/**
+ * Autocrop same color borders from this image.
+ * All borders must be of the same color as the top left pixel, to be cropped.
+ * It should be possible to crop borders each with a different color,
+ * but since there are many ways for corners to intersect, it would
+ * introduce unnecessary complexity to the algorithm.
+ * @param (optional) cb a callback for when complete
+ * @returns this for chaining of methods
+ */
+Jimp.prototype.autocrop = function (cb) {
+    var w = this.bitmap.width;
+    var h = this.bitmap.height;
+    var northPixelsToCrop = 0;
+    var eastPixelsToCrop = 0;
+    var southPixelsToCrop = 0;
+    var westPixelsToCrop = 0;
+
+    var color = this.getPixelColor(0, 0); // get top left pixel color
+
+    // scan each side for same color borders
+    north: // north side
+    for (var y = northPixelsToCrop; y < h - (northPixelsToCrop + southPixelsToCrop); y++) {
+        for (var x = westPixelsToCrop; x < w - (eastPixelsToCrop + westPixelsToCrop); x++) {
+            if (this.getPixelColor(x, y) !== color) {
+                // this pixel is not the same color as the first one: abort this side scan
+                break north;
+            }
+        }
+        // this row contains all pixels with the same color: increment this side pixels to crop
+        northPixelsToCrop++;
+    }
+
+    east: // east side
+    for (var x = westPixelsToCrop; x < w - (eastPixelsToCrop + westPixelsToCrop); x++) {
+        for (var y = northPixelsToCrop; y < h - (northPixelsToCrop + southPixelsToCrop); y++) {
+            if (this.getPixelColor(x, y) !== color) {
+                // this pixel is not the same color as the first one: abort this side scan
+                break east;
+            }
+        }
+        // this column contains all pixels with the same color: increment this side pixels to crop
+        eastPixelsToCrop++;
+    }
+
+    south: // south side
+    for (var y = h - 1; y >= 0; y--) {
+        for (var x = w - 1; x >= 0; x--) {
+            if (this.getPixelColor(x, y) !== color) {
+                // this pixel is not the same color as the first one: abort this side scan
+                break south;
+            }
+        }
+        // this row contains all pixels with the same color: increment this side pixels to crop
+        southPixelsToCrop++;
+    }
+
+    west: // west side
+    for (var x = w - 1; x >= 0; x--) {
+        for (var y = h - 1; y >= 0; y--) {
+            if (this.getPixelColor(x, y) !== color) {
+                // this pixel is not the same color as the first one: abort this side scan
+                break west;
+            }
+        }
+        // this column contains all pixels with the same color: increment this side pixels to crop
+        westPixelsToCrop++;
+    }
+
+    // safety checks
+    var widthOfPixelsToCrop = w - (westPixelsToCrop + eastPixelsToCrop);
+    widthOfPixelsToCrop >= 0 ? widthOfPixelsToCrop : 0;
+    var heightOfPixelsToCrop = h - (southPixelsToCrop + northPixelsToCrop);
+    heightOfPixelsToCrop >= 0 ? heightOfPixelsToCrop : 0
+
+    // crop image 
+    this.crop(
+        westPixelsToCrop,
+        northPixelsToCrop,
+        widthOfPixelsToCrop,
+        heightOfPixelsToCrop
+    );
+
+    if (isNodePattern(cb)) return cb.call(this, null, this);
+    else return this;
+};
+
 /**
  * Blits a source image on to this image
  * @param src the source Jimp instance

test/autocrop.js

@@ -0,0 +1,77 @@
+var Jimp = require("../index.js");
+
+var imageBase = "peace.png";
+var imageTransparent = "peace-transparent.png";
+var imageWithOneColorBorder = "peace-with-border.png";
+var imageWithManyColorsBorder = "peace-with-different-borders.png";
+
+/*
+new Jimp(imageWithOneColorBorder, function (err, image) {
+	if (err) {
+  	  	return console.error("Error reading image", imageWithOneColorBorder, ":", err);
+   	}
+    this.autocrop();
+    this.write("./output/" + imageWithOneColorBorder, function() {
+
+        var p1 = Jimp.read(imageBase);
+        var p2 = Jimp.read("./output/" + imageWithOneColorBorder);
+
+        Promise.all([p1, p2]).then(function(images) {
+
+            // compare image and imageWithOneColorBorder after autocrop for() equality
+            var distance = Jimp.distance(images[0], images[1]);
+            if (distance !== 0) {
+                console.error("imageWithOneColorBorder after autocrop() differs by imageBase!");
+            }
+        }).catch(function (err) {
+            console.error('t1:', err);
+        });
+    });
+});
+*/
+new Jimp(imageTransparent, function (err, image) {
+    if (err) {
+        return console.error("Error reading image", imageTransparent, ":", err);
+    }
+    this.autocrop();
+    this.write("./output/" + imageTransparent, function() {
+
+        var p1 = Jimp.read(imageBase);
+        var p2 = Jimp.read("./output/" + imageTransparent);
+
+        Promise.all([p1, p2]).then(function(images) {
+
+            // compare image and imageTransparent after autocrop for() inequality
+            var distance = Jimp.distance(images[0], images[1]);
+            if (distance === 0) {
+                console.error("imageTransparent after autocrop() does not differ from imageBase!");
+            }
+        }).catch(function (err) {
+            console.error(err);
+        });
+    });
+});
+return;
+
+new Jimp(imageWithManyColorsBorder, function (err, image) {
+	if (err) {
+		return console.error("Error reading image", imageWithManyColorsBorder, ":", err);
+	}
+    this.autocrop();
+    this.write("./output/" + imageWithManyColorsBorder, function() {
+
+        var p1 = Jimp.read(imageBase);
+        var p2 = Jimp.read("./output/" + imageWithManyColorsBorder);
+
+        Promise.all([p1, p2]).then(function(images) {
+
+            // compare image and imageWithManyColorsBorder after autocrop for() inequality
+            var distance = Jimp.distance(images[0], images[1]);
+            if (distance === 0) {
+                console.error("imageWithManyColorsBorder after autocrop() does not differ from imageBase!");
+            }
+        }).catch(function (err) {
+            console.error(err);
+        });
+    });
+});

test/tests.sh

@@ -11,41 +11,45 @@ function clean {
 }
 
 clean
-echo "promise.js (1/9)"
+echo "promise.js (1/10)"
 node promise.js
 
 clean
-echo "callbacks.js (2/9)"
+echo "callbacks.js (2/10)"
 node callbacks.js
 
 clean
-echo "chained.js (3/9)"
+echo "chained.js (3/10)"
 node chained.js
 
 clean
-echo "create.js (4/9)"
+echo "create.js (4/10)"
 node create.js
 
 clean
-echo "rotation.js (5/9)"
+echo "rotation.js (5/10)"
 node rotation.js
 
 clean
-echo "filetype.js (6/9)"
+echo "filetype.js (6/10)"
 node filetypes.js
 
 clean
-echo "color.js (7/9)"
+echo "color.js (7/10)"
 node color.js
 
 clean
-echo "compare.js (8/9)"
+echo "compare.js (8/10)"
 node compare.js
 
 clean
-echo "exif.js (9/9)"
+echo "exif.js (9/10)"
 node exif.js
 
+clean
+echo "autocrop.js (10/10)"
+node autocrop.js
+
 
 
 clean