TweetFollow Us on Twitter

September 94 - GRAPHICAL TRUFFLES

GRAPHICAL TRUFFLES

A Cool QuickDraw GX Clipping Effect

PETE ("LUKE") ALEXANDER

[IMAGE Graphical_Truffles_final_1.GIF]

Wading through the vast sea of documentation you get with the QuickDraw GX Software Developer's Kit, you may not realize all the cool things this new graphics model lets you do. In this column, we'll look at just one of those cool things: clipping one shape to the inside of another arbitrary shape. As an illustration, we'll take a bitmapped image of a tropical beach (Figure 1) and clip it to the word "BAY" (Figure 2). Figure 3 shows the result. There's a sample application and source code on this issue's CD.

CREATING THE SHAPES
We'll be collecting the results of our operations into a picture shape. We'll assume that the QuickDraw GX environment has already been set up and that we have a window ready to draw into.

For information on setting up the QuickDraw GX environment, see "Getting Started With QuickDraw GX" in develop Issue 15. The full details are in Inside Macintosh: QuickDraw GX Objects and Inside Macintosh: QuickDraw GX Graphics. *

We start by creating an empty picture to which we can add shapes:

gxShape  thePicture;
thePicture = GXNewShape(gxPictureType);

The bitmap shape we'll be clipping (Figure 1) is stored in our application's resource fork as a 'pxmp' resource. We retrieve it with the GetPixMapShape call from the qd library.

[IMAGE Graphical_Truffles_final_2.GIF]

Figure 1. The shape to be clipped

gxShape theBitmap;
theBitmap = GetPixMapShape(kPixMapID);

To create the clip shape, we start with a text shape containing the word BAY.

gxShape theClip;
theClip = GXNewText(3, (unsigned char*)"BAY", nil);

[IMAGE Graphical_Truffles_final_3.GIF]

Figure 2. The clip shape

[IMAGE Graphical_Truffles_final_4.GIF]

Figure 3. Result of clipping Figure 1 to Figure 2

POSITIONING AND SCALING THE TEXT SHAPE
Before we set our text shape to be the clip of our bitmap shape, we need to move it to the top left corner of the bitmap shape and then scale it to encompass the entire bitmap.

We'll look at two ways to do this. The first method takes us through all the steps in the process, while the second is simpler and lets QuickDraw GX do more of the work for us.

The origin of a text shape is on the baseline, but in this case, because there are no descenders in the text, we just use the bottom left corner of the shape's bounds. We need to offset the text shape by its own height from the top of the bitmap shape. So we need to know the bounds of both the bitmap shape (to find the coordinates of its top left corner) and the text shape (to calculate its height):

gxRectangle	bitmapBounds, textBounds;
GXGetShapeBounds(theBitmap, 0, &bitmapBounds);
GXGetShapeBounds(theClip, 0, &textBounds);
textHeight = textBounds.bottom - textBounds.top;
GXMoveShapeTo(theClip, bitmapBounds.left, 
		bitmapBounds.top + textHeight);

Our original text shape, which is the default text size of 12 points, isn't big enough to cover the entire bitmap shape. If we were to do the clipping at this point, we would get just a tiny piece of the corner instead of the whole bitmap. To get the whole thing, we have to scale the text shape to match the size of the bitmap shape.

For the text shape to scale linearly, without taking the font's hinting into account, we have to turn off QuickDraw GX's built-in metrics and contour grid-fitting capabilities. We do this by setting the shape's text attributes as follows:

GXSetShapeTextAttributes(theClip,
	gxNoMetricsGridText | gxNoContourGridText);

Although QuickDraw GX lets us clip to any arbitrary shape, clipping is actually limited to primitive shapes only. That is, the clip shape must be a shape whose geometry and fill properties by themselves define the shape; primitive shapes don't use information from a style or transform object. This is not a problem, though, because we can easily convert a shape to its primitive form. The following call does the job:

GXPrimitiveShape(theClip);

The result is a filled path shape (which is a primitive shape) representing the outlines of the letters in the word BAY.

Next we need to determine how much to scale the text shape to encompass the entire bitmap shape. We do this by finding the width and height of both shapes' bounds rectangles and scaling the text shape in each direction by the ratio between the two:

Fixed 		bitmapWidth, bitmapHeight;
Fixed 		textWidth, textHeight;
Fixed 		xScale, yScale;

// Determine the width ratio.
bitmapWidth = bitmapBounds.right - bitmapBounds.left;
textWidth = textBounds.right - textBounds.left;
xScale = FixedDivide(bitmapWidth, textWidth);

// Determine the height ratio.
bitmapHeight = bitmapBounds.bottom - bitmapBounds.top;
textHeight = textBounds.bottom - textBounds.top;
yScale = FixedDivide(bitmapHeight, textHeight);

GXScaleShape(theClip, xScale, yScale,
			bitmapBounds.left, bitmapBounds.top);

We've now scaled the text shape to encompass the entire area of our bitmap shape, and we're ready to use it to clip the bitmap shape. But it turns out that there's a shorter way to do this; we can actually accomplish the same thing with only three lines of code:

GXSetShapeTextAttributes(theClip,
    gxNoMetricsGridText | gxNoContourGridText);
GXGetShapeBounds(theBitmap, 0, &textBounds);
GXSetShapeBounds(theClip, &textBounds);

As in the earlier method, we turn hinting off and get the bounds of our bitmap shape. The magic here is in the GXSetShapeBounds call: when applied to typographic shapes, this call positions and scales the text to the new bounds and converts it to a primitive shape. That's it! QuickDraw GX does the hard work for us automatically, and we're ready to set the clip of our bitmap shape.

SETTING THE CLIP SHAPE
Now that the text shape is positioned and scaled the way we want it, we're ready to set it up as the clip of our bitmap shape:

GXSetShapeClip(theBitmap, theClip);

This call changes the clip shape contained within the transform used by our bitmap shape, replacing it with the new clip shape that we've created.

If the same transform were being shared by other shapes, QuickDraw GX would make a copy of the transform to associate with our bitmap shape, ensuring that the new clip would not affect any of the other shapes sharing the same transform.*The next step is to add the clipped bitmap shape to our picture with GXSetPictureParts. (Note that we could also use the library call AddToShape or the core call GXSetShapeParts to do the same thing, but I chose to be more explicit here.)

GXSetPictureParts(thePicture, 0, 0, 1, &theBitmap,
		nil, nil, nil);

The picture now contains a new reference to the original bitmap shape, complete with the new clip we've added to it. Once there's a reference to it in the picture, we don't need the original reference anymore, so we dispose of it:

GXDisposeShape(theBitmap);

DRAWING THE OUTLINE
The last order of business is to draw an outline around the clipped bitmap. We can accomplish this by setting up the drawing characteristics of our scaled text shape to draw the outline and then adding it to our picture. To frame the shape with a closed outline, we set its fill characteristic to gxClosedFrameFill. Since we want the frame to lie outside the geometry of the shape, we set its style attributes to gxOutsideFrameStyle. Finally, we set the pen size to 3 to get a satisfyingly fat outline, and we set the color of the outline to blue:

GXSetShapeFill(theClip, gxClosedFrameFill);
GXSetShapeStyleAttributes(theClip, gxOutsideFrameStyle);
GXSetShapePen(theClip, ff(3));
SetShapeCommonColor(theClip, blue);

Now we can add the outlined shape to our picture and dispose of it, as before:

GXSetPictureParts(thePicture, 0, 0, 1, &theClip,
		nil, nil, nil);
GXDisposeShape(theClip);

DRAWING THE PICTURE
Before drawing our picture, we'll move it down a little from the top left corner of the window. We could do this by retrieving the picture's transform and shifting it down and to the right with GXMoveTransform; however, since the gxMapTransformShape attribute is set for pictures by default, we can just call GXMoveShape:

GXMoveShape(thePicture, f(20), ff(15));

Finally, we're ready to draw the picture:

GXDrawShape(thePicture);

We're done! The result should look like Figure 3.

THAT'S ALL, FOLKS
You've had a quick look at one of the many cool things you can do with the QuickDraw GX graphics system. As you can see from this example, the power and flexibility of QuickDraw GX can give your application the ability to do things you could only dream about until now.

PETE ("LUKE") ALEXANDERRegular readers of Luke's columns will know that he took his sabbatical from Apple this summer. He sent us a postcard: "Hey dudes! While you're looking out your windows at Silicon Valley smog, I'm looking out my windows at the rocky faces of Montana. Have you heard of National Parks? They're places of unusual beauty set apart from development. Not that kind of development! The kind that causes smog. At Yellowstone Park I enjoyed the clear air, I found where the buffalo roam, and I learned why they call it Old Faithful. I'm now flying somewhere over Montana (don't worry, I'm steering with my knee), admiring the mountains with their lingering snow and enjoying the wide open spaces. Oops, mountain ahead and no more room on the card." He signed it, "See you later, Luke" but then crossed out the "See you later." We're worried, really worried.*

Thanks to Hugo Ayala and Cary Clark for reviewing this column. *

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

ExpanDrive 5.4.1 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
Espionage 3.6.6 - Simple, state-of-the-a...
Espionage offers state-of-the-art encryption and plausible deniability for your confidential data. Sometimes, encrypting your data isn't enough to protect it. That's why Espionage 3 goes beyond data... Read more
Pinegrow Web Designer 2.94 - Mockup and...
Pinegrow Web Designer is desktop app that lets you mockup and design webpages faster with multi-page editing, CSS and LESS styling, and smart components for Bootstrap, Foundation, Angular JS, and... Read more
1Password 6.3.3 - Powerful password mana...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
Sublime Text 3126 - Sophisticated text e...
Sublime Text is a sophisticated text editor for code, markup, and prose. You'll love the slick user interface, extraordinary features, and amazing performance. Features Goto Anything. Use Goto... Read more
ForkLift 3.0 Beta 2 - Powerful file mana...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
OmniFocus 2.7.1 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
CleanApp 5.1.1 - Application deinstaller...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Together 3.6.1 - Store and organize all...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Features Smart storage. With simple drag-and-drop... Read more
Cloud 4.1.1 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more

5 great apps for the budget traveller
Travelling abroad, or even within your home country, has never been easier thanks to our handy smartphone companions. There are hundreds of apps on the market that promise to make your world journeys hassle-free, but we've selected five of the... | Read more »
Zip—Zap (Games)
Zip—Zap 1.01 Device: iOS Universal Category: Games Price: $1.99, Version: 1.01 (iTunes) Description: Touch to contract.Release to let go.Bring the clumsy mechanical beings home. · · · over 100 levelsno adsno in-app-purchases Zip—... | Read more »
Paperback: The Game (Games)
Paperback: The Game 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: You are an author trying to finish kitschy paperback novels. Complete Westerns, Science Fiction, Romance or even a Crime... | Read more »
How to Rule With a Firm Hand in My Majes...
My Majesty is a kingdom management sim not unlike August’s magisterial hit, Reigns. It’s essentially a reskin of developer Tigrido’s previous management sim, Dictator. As supreme ruler of the land, you must consult with a number of subjects to... | Read more »
Our 5 Favorite iMessage Sticker Packs
At long last, iMessage joins the ranks of messaging apps the likes of LINE and Whatsapp, adding an impressive collection of stickers. They’re a great way to add a little something extra to your daily conversations. [Read more] | Read more »
How to get past Vulture Island's tr...
Vulture Island is a colorful and quirky mish-mash of platforming and puzzles. It’s creative and fresh, but sometimes the game can throw a curveball at you, leaving you stuck as to how you should progress. These tips will help you explore smoothly... | Read more »
The new Clash of Kings is just for Weste...
If you’ve played the original Clash of Kings, you’ll probably recognise the city building, alliance forging and strategic battles in Clash of Kings: The West. What sets this version apart is that it’s tailor made for a Western audience and the... | Read more »
Frost - Survival card game (Games)
Frost - Survival card game 1.12.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.12.1 (iTunes) Description: *Warning: the game will work on iPhone 5C and above and iPad Pro / 4. Other devices are not supported* | Read more »
How to build and care for your team in D...
Before you hit the trail and become a dog sledding legend, there’s actually a fair bit of prep work to be done. In Dog Sled Saga, you’re not only racing, you’re also building and caring for a team of furry friends. There’s a lot to consider—... | Read more »
How to win every race in Dog Sled Saga
If I had to guess, I’d say Dog Sled Saga is the most adorable racing game on the App Store right now. It’s a dog sled racing sim full of adorable, loyal puppies. Just look at those fluffy little tails wagging. Behind that cute, pixelated facade is... | Read more »

Price Scanner via MacPrices.net

Aetna to Transform Members’ Consumer Health E...
Health care benefits company Aetna, which has an estimated 46.3 million clients, today announced a new initiative to revolutionize members consumer health experience by combining the power of iOS... Read more
USB-IF Announces USB Audio Device Class 3.0 S...
USB Implementers Forum (USB-IF), the support organization for the advancement and adoption of USB technology, today announced the USB Audio Device Class 3.0 specification to establish USB Audio over... Read more
Clearance 12-inch 1.2GHz Retina MacBooks, App...
Apple has Certified Refurbished 2015 12″ 1.2GHz Retina MacBooks available for $1189, or $410 off original MSRP. Apple will include a standard one-year warranty with each MacBook, and shipping is free... Read more
Logitech SmartDock and Skype For Business Com...
Logitech has announced Logitech SmartDock, an AV meeting room solution designed in collaboration with Microsoft. Logitech SmartDock works with Skype for Business and qualified devices, including... Read more
27-inch iMacs on sale for up to $220 off MSRP
B&H Photo has 27″ Apple iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $1899.99 $... Read more
Apple Macs and iPads available for up to $300...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more
Mac Pros on sale for up to $200 off MSRP
B&H Photo has Mac Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2899, $100 off MSRP - 3.5GHz 6-core Mac Pro: $3799, $... Read more
15-inch 2.2GHz Retina MacBook Pro on sale for...
B&H Photo has the 2015 15″ 2.2GHz Retina MacBook Pro (MJLQ2LL/A) on sale for $1799, including free shipping plus NY sales tax only. Amazon also has the 2015 15″ 2.2GHz Retina MacBook Pro (... Read more
Toughbook Celebrates 20 Years of Ruggedized M...
Panasonic System Communications Company of North America, Division of Panasonic Corporation of North America (Panasonic) today celebrates the 20th anniversary of its industry-leading Toughbook mobile... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
Sr. *Apple* Mac Engineer - Net2Source Inc....
…staffing, training and technology. We have following position open with our client. Sr. Apple Mac Engineer6+ Months CTH Start date : 19th Sept Travelling Job If Read more
*Apple* Retail - Multiple Positions-Norfolk,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.