Add podspec, update README

README.md

@@ -5,7 +5,11 @@ Category for trimming transparent pixels of an UIImage object.
 
 How to use
 ----------
-Add the `UIImage+Trim` files to your project. Include `UIImage+Trim.h` in the files where you want to trim your images. 
+Add `UIImage+Trim` to your project with Cocoapods:
+
+`pod 'UIImage-Trim', :git => 'https://github.com/gizmosachin/UIImage-Trim'`
+
+Include `UIImage+Trim.h` in the files where you want to trim your images. 
 
 Trimming is pretty straightforward:
 

UIImage+Trim.h → Source/UIImage+Trim.h

@@ -14,5 +14,6 @@
 - (UIEdgeInsets)transparencyInsetsRequiringFullOpacity:(BOOL)fullyOpaque;
 - (UIImage *)imageByTrimmingTransparentPixels;
 - (UIImage *)imageByTrimmingTransparentPixelsRequiringFullOpacity:(BOOL)fullyOpaque;
+- (UIImage *)imageByTrimmingWhitePixelsWithOpacity:(UInt8)tolerance;
 
 @end

UIImage+Trim.m → Source/UIImage+Trim.m

@@ -28,7 +28,7 @@ - (UIEdgeInsets)transparencyInsetsRequiringFullOpacity:(BOOL)fullyOpaque
 	uint8_t * bitmapData = calloc((size_t)(width * height), sizeof(uint8_t));
 
 	// Create alpha-only bitmap context
-	CGContextRef contextRef = CGBitmapContextCreate(bitmapData, (NSUInteger)width, (NSUInteger)height, 8, (NSUInteger)bytesPerRow, NULL, kCGImageAlphaOnly);
+	CGContextRef contextRef = CGBitmapContextCreate(bitmapData, (NSUInteger)width, (NSUInteger)height, 8, (NSUInteger)bytesPerRow, NULL, (kCGBitmapAlphaInfoMask & kCGImageAlphaOnly));
 
 	CGImageRef cgImage = self.CGImage;
 	CGRect rect = CGRectMake(0, 0, width, height);
@@ -172,4 +172,139 @@ - (UIImage *)imageByTrimmingTransparentPixelsRequiringFullOpacity:(BOOL)fullyOpa
     return img;
 }
 
+/*
+ * Calculates the insets of white area around all sides of the image
+ *
+ * @param tolerance
+ *        Maximal difference from white
+ */
+- (UIEdgeInsets)transparencyInsetsByCuttingWhitespace:(UInt8)tolerance
+{
+	// Draw our image on that context
+	NSInteger width  = (NSInteger)CGImageGetWidth([self CGImage]);
+	NSInteger height = (NSInteger)CGImageGetHeight([self CGImage]);
+	NSInteger bytesPerRow = width * (NSInteger)sizeof(uint8_t);
+
+	// Allocate array to hold alpha channel
+	uint8_t * bitmapData = calloc((size_t)(width * height), sizeof(uint8_t));
+
+	// Create grayscale image
+    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
+	CGContextRef contextRef = CGBitmapContextCreate(bitmapData, (NSUInteger)width, (NSUInteger)height, 8, (NSUInteger)bytesPerRow, colorSpace, (kCGBitmapAlphaInfoMask & kCGImageAlphaNone));
+
+	CGImageRef cgImage = self.CGImage;
+	CGRect rect = CGRectMake(0, 0, width, height);
+	CGContextDrawImage(contextRef, rect, cgImage);
+
+	// Sum all non-transparent pixels in every row and every column
+	uint16_t * rowSum = calloc((size_t)height, sizeof(uint16_t));
+	uint16_t * colSum = calloc((size_t)width,  sizeof(uint16_t));
+
+	// Enumerate through all pixels
+	for (NSInteger row = 0; row < height; row++) {
+
+		for (NSInteger col = 0; col < width; col++) {
+
+            // Found darker pixel
+            if (bitmapData[row*bytesPerRow + col] <= UINT8_MAX - tolerance) {
+
+                rowSum[row]++;
+                colSum[col]++;
+
+            }
+		}
+	}
+
+	// Initialize crop insets and enumerate cols/rows arrays until we find non-empty columns or row
+	UIEdgeInsets crop = UIEdgeInsetsZero;
+
+    // Top
+	for (NSInteger i = 0; i < height; i++) {
+
+		if (rowSum[i] > 0) {
+
+			crop.top = i;
+            break;
+
+		}
+
+	}
+
+    // Bottom
+	for (NSInteger i = height - 1; i >= 0; i--) {
+
+		if (rowSum[i] > 0) {
+			crop.bottom = MAX(0, height - i - 1);
+            break;
+		}
+
+	}
+
+    // Left
+	for (NSInteger i = 0; i < width; i++) {
+
+		if (colSum[i] > 0) {
+			crop.left = i;
+            break;
+		}
+
+	}
+
+    // Right
+	for (NSInteger i = width - 1; i >= 0; i--) {
+
+		if (colSum[i] > 0) {
+
+			crop.right = MAX(0, width - i - 1);
+            break;
+
+		}
+	}
+
+	free(bitmapData);
+	free(colSum);
+	free(rowSum);
+
+    CGContextRelease(contextRef);
+
+	return crop;
+}
+
+- (UIImage *)imageByTrimmingWhitePixelsWithOpacity:(UInt8)tolerance
+{
+	if (self.size.height < 2 || self.size.width < 2) {
+
+		return self;
+
+	}
+
+	CGRect rect = CGRectMake(0, 0, self.size.width * self.scale, self.size.height * self.scale);
+	UIEdgeInsets crop = [self transparencyInsetsByCuttingWhitespace:tolerance];
+
+    UIImage *img = self;
+
+	if (crop.top == 0 && crop.bottom == 0 && crop.left == 0 && crop.right == 0) {
+
+		// No cropping needed
+
+	} else {
+
+		// Calculate new crop bounds
+		rect.origin.x += crop.left;
+		rect.origin.y += crop.top;
+		rect.size.width -= crop.left + crop.right;
+		rect.size.height -= crop.top + crop.bottom;
+
+		// Crop it
+		CGImageRef newImage = CGImageCreateWithImageInRect([self CGImage], rect);
+
+		// Convert back to UIImage
+        img = [UIImage imageWithCGImage:newImage scale:self.scale orientation:self.imageOrientation];
+
+        CGImageRelease(newImage);
+	}
+
+    return img;
+}
+
 @end

UIImage-Trim.podspec

@@ -0,0 +1,12 @@
+Pod::Spec.new do |s|
+  s.name     = 'UIImage-Trim'
+  s.authors = { "Sachin Patel" => "me@gizmosachin.com" }
+  s.license = 'MIT'
+  s.summary = 'Category for trimming transparent pixels of an UIImage object.'
+  s.version  = '1.0'
+  s.homepage = 'https://github.com/gizmosachin/UIImage-Trim'
+  s.source = { :git => "https://github.com/gizmosachin/UIImage-Trim.git", :tag => '1.0' }
+  s.frameworks = 'Foundation', 'UIKit'
+  s.platform = :ios, '7.0'
+  s.source_files = 'Source'
+end