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Rotate NSImage in an NSImageView

09-12-09 11:41 Filed in: Cocoa | Objective C | Programming - 编程 | Snippet - 小片

I didn’t want to half-implement the new tab feature in Slider – I want people to have almost as much control as if they were coding the site by hand.

This has meant I’ve had to rethink Slider’s UI many times, and I’ve had (re: couldn’t face shipping without) to implement many small features that I feel are required, from a usability standpoint.

When I decided that the user may choose to place tabs in 12 different positions, I needed to consider how this would effect the arrows and sliding animations. I came to the conclusion that if the user elects to place the tabs on the top or bottom, the arrows will be on the left and right, with the animation going right/left. If the user chooses to place tabs on the left or right, the arrows will be positioned on the top and bottom, with the animation going up/down.

Pictures make it easier:

tab_position

tab_position_1

As soon as I implemented this I realised how much of a pain it would be to copy out the arrow images, rotate them in an external program, then copy them back in. So I put some buttons next to the arrow image wells that allow the user to rotate the arrows within Slider itself.

Here is the code I used to rotate the images (thanks to Jerry Krinock and Steve Christensen and for posting this solution to the Cocoa-dev list):

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#import <Cocoa/Cocoa.h>
 
@interface NSImage (Transform)
 
 
/*!
 @brief    Rotates an image around its center by a given
 angle in degrees and returns the new image.
 
 @details  The width and height of the returned image are,
 respectively, the height and width of the receiver.
 
 I have not yet tested this with a non-square image.
 
authors: Jerry Krinock and Steve Christensen
 */
- (NSImage*)imageRotatedByDegrees:(CGFloat)degrees ;
 
@end
 
#import "NSImage+Transform.h"
 
@implementation NSImage (Transform)
 
 
- (NSImage*)imageRotatedByDegrees:(CGFloat)degrees {
 
	// calculate the bounds for the rotated image
    NSRect imageBounds = {NSZeroPoint, [self size]};
 
	NSBezierPath* boundsPath = [NSBezierPath bezierPathWithRect:imageBounds];
 
    NSAffineTransform* transform = [NSAffineTransform transform];
 
    [transform rotateByDegrees:degrees];
    [boundsPath transformUsingAffineTransform:transform];
 
    NSRect rotatedBounds = {NSZeroPoint, [boundsPath bounds].size};
 
	NSImage* rotatedImage = [[NSImage alloc] initWithSize:rotatedBounds.size];
 
    // center the image within the rotated bounds
 
	imageBounds.origin.x = NSMidX(rotatedBounds) - (NSWidth (imageBounds) / 2); imageBounds.origin.y = NSMidY(rotatedBounds) - (NSHeight (imageBounds) / 2);
 
    // set up the rotation transform
    transform = [NSAffineTransform transform];
 
	[transform translateXBy:+(NSWidth(rotatedBounds) / 2) yBy:+ (NSHeight(rotatedBounds) / 2)];
 
    [transform rotateByDegrees:degrees];
 
	[transform translateXBy:-(NSWidth(rotatedBounds) / 2) yBy:- (NSHeight(rotatedBounds) / 2)];
 
    // draw the original image, rotated, into the new image
    [rotatedImage lockFocus];
    [transform concat];
 
	[self drawInRect:imageBounds fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0] ;
 
    [rotatedImage unlockFocus];
 
    return [rotatedImage autorelease];	
 
}
@end

I had to change (from/to):

NSImage* rotatedImage = [[[NSImage alloc] initWithSize:rotatedBounds.size] autorelease];
 NSImage* rotatedImage = [[NSImage alloc] initWithSize:rotatedBounds.size];
return rotatedImage;
return [rotatedImage autorelease];
[transform set];
[transform concat];

For it to work flawlessly with Slider.

Thanks guys!

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How to Prevent Noisy NSBitmapImageReps

09-11-10 13:00 Filed in: Cocoa | Objective C | Programming - 编程

Before

Images generated for Slider’s background and tabs contained a lot of noise – random ugly pixels throughout the images.

I was unsure why this was happening, so I asked the Cocoa-Dev mailing list.

Rob Keniger kindly replied with the following solution:

“An NSBitmapImageRep is not guaranteed to be empty when you create it and in general it’s just full of random bits. You need to clear it explicitly if you are drawing non-opaque content”

He included the following snippet that solved my problem nicely:

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- (void) clearBitmapImageRep:(NSBitmapImageRep *)bitmap {
   unsigned char* bitmapData = [bitmap bitmapData];
   if (bitmapData != NULL)
   {
       bzero(bitmapData, [bitmap bytesPerRow] * [bitmap pixelsHigh]);
   }
}

I call it as soon as I’ve created a new NSBitmapImageRep, like so:

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NSBitmapImageRep  *theImage = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:imageSize.width pixelsHigh:imageSize.height
                            bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO
                            colorSpaceName:NSDeviceRGBColorSpace bytesPerRow:0 bitsPerPixel:0];
 
[self clearBitmapImageRep:theImage];

This results in noise-free images.

After

Thanks Rob!










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The Mutations of Slider’s Tab Option Pane

09-11-09 20:46 Filed in: Cocoa | Objective C | Programming - 编程 | Rapidweaver | Slider

During the past week, I’ve been working on Slider’s new Tab option pane.

I took screen shots before making changes to the layout.

Here they are:

Tabs Iteration #1

Tabs Iteration #2

Tabs Iteration #3

Tabs Iteration #4

I hope I’m not tempted to change things around again… I really need to get the backend going now!

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Accessing Primitives From NSDictionarys in Cocoa…

09-11-07 22:23 Filed in: Cocoa | Objective C

This “gotcha” had me scratching my head for a little while.

Edit: this “gotcha” stemmed more from my inexperience with Cocoa than anything else. NSDictionaries store only objects, one shouldn’t try to insert int/float/bool etc into one. Instead use NSNumber for these values. Duh.

When storing various NSObjects in an NSMutableDictionary, I assumed one would access (in this case the object being stored is an NSColor) them like:

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[[dictionary objectForKey:idle_TabBorderAllColourKey] color]

I also assumed that one would access “int”, “float” and other primitives like:

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[dictionary objectForKey:idle_TabBorderAllWidthKey]

After writing, compiling and attempting run my code, however, I discovered that I was wrong.

It should be done like so:

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[dictionary objectForKey:idle_TabBorderAllColourKey]

For NSObjects, and:

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[[dictionary objectForKey:idle_TabBorderAllWidthKey] intValue]

for primitives.

Cocoa noob learns more about Cocoa with each passing minute!

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Slider Progress: Slider Styling Option Pane

09-11-03 20:51 Filed in: Cocoa | Objective C | Programming - 编程 | Rapidweaver | Slider

During the great rewrite, I’ve been trying to focus on one section at a time. The first section to come under attack was “everything pertaining to the styling of Slider that is not Arrow-related”. After much mucking-about I decided to combine the Border, Rounded Corner, Background Image, Gradient and Background Colour onto one Pane.

I don’t know why I didn’t do this before, it is obvious and really the only logical way to present these controls – enabling some may disable others, it was confusing and clumsy when they were on different tabs.

Now users will be able to see what is being enabled/disabled without swapping between different tabs.

Here is a screenshot of the option page as it is currently:

Slider style configuration laid bare: Click to view

Slider style configuration laid bare: Click to view

This is about the 10th layout redesign, I’m quite sure there will be no major changes from now on.

Still a long way to go, but progress *is* being made.

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Tile an NSImage Within an NSBezierPath

09-10-27 19:41 Filed in: Cocoa | Objective C | Programming - 编程 | Snippet - 小片 | Tutorial - 教程

Another snippet I had to write during the great Slider rebuild.

I needed to be able to take an NSImage supplied by the user and tile it within an NSBezierPath defined by more user-set values.

The below example uses a rounded rectangle.

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NSBitmapImageRep *theImage = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:imageSize.width pixelsHigh:imageSize.height
 bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO
 colorSpaceName:NSDeviceRGBColorSpace bytesPerRow:0 bitsPerPixel:0];
 
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:theImage]];
 
//bgImage can be any NSImage
NSColor *c = [NSColor colorWithPatternImage:bgImage];
[c set];
[path appendBezierPathWithRoundedRect:NSMakeRect(0, 0, imageSize.width, imageSize.height) xRadius:10.0 yRadius:10.0];
[path fill];
 
[NSGraphicsContext restoreGraphicsState];

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Fill a Path With A Scaled Image, Ignoring Image Proportions

09-10-27 19:19 Filed in: Cocoa | Objective C | Programming - 编程 | Tutorial - 教程

While continuing to rebuild Slider’s background image features, I was forced to rewrite the code that scales an image up/down to Slider’s portal size, ignoring the image’s original proportions. The image also had to be painted within a path, as Slider may have differently shaped corners compared to the image to be scaled.

The below code accomplishes the scaling and painting of the image.

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//theImage = the resulting image, that will have a scaled (proportions ignored) version of "bgImage" painted onto it
NSBitmapImageRep *theImage = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:imageSize.width pixelsHigh:imageSize.height
 bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO
 colorSpaceName:NSDeviceRGBColorSpace bytesPerRow:0 bitsPerPixel:0];
 
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:theImage]];
 
NSImage bg = [[NSImage alloc] initWithSize: imageSize];
 
//bgImage can be any NSImage
NSSize originalSize = [bgImage size];
[bg lockFocus];
[bgImage drawInRect: NSMakeRect(0, 0, imageSize.width, imageSize.height) 
fromRect: NSMakeRect(0, 0, originalSize.width, originalSize.height) 
operation: NSCompositeSourceOver fraction: 1.0];
 
[bg unlockFocus];
 
NSColor *c = [NSColor colorWithPatternImage:bg];
[c set];
[path appendBezierPathWithRoundedRect:NSMakeRect(0, 0, imageSize.width, imageSize.height) xRadius:10.0 yRadius:10.0];
[aPath fill];
 
[NSGraphicsContext restoreGraphicsState];

“path” could be any NSBezierPath.

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