TweetFollow Us on Twitter

Winter 92 - GRAPHICS HINTS FROM FORREST

GRAPHICS HINTS FROM FORREST

USING THE PALETTE MANAGER OFF-SCREEN

FORREST TANAKA

[IMAGE 029-030_Tanaka_column_re1.GIF]


Most people who've done any graphics programming on the Macintosh are aware of the Palette Manager, because it's the documented way to control the on-screen color environment, and perhaps because my cohorts and I in Developer Technical Support keep going on about how right the world would be if everyone used it. In an effort to follow the rules as best they can, some people have taken the Palette Manager so much to heart that they use it not only with windows, but with off-screen cGrafPorts as well--something that isn't heard about very much. Some of these people have concluded that all the features of the Palette Manager apply just as well to off-screen cGrafPorts as they do to windows. Logical enough, right?

Well, that's the kick; whether this is logical or not, the truth is that only a small part of the Palette Manager works with off-screen cGrafPorts. Specifically, the pmCourteous usage mode and the pmWhite and pmBlack usage-mode modifiers work fine when they're used in a palette that's attached to an off-screen cGrafPort, but the pmTolerant, pmAnimated, and pmExplicit usage modes do not. In this column, I'll describe how you can take advantage of the Palette Manager features that work off-screen and how you can simulate the features that don't work.

The pmCourteous usage mode seems pretty useless to a lot of people because it has no effect on the current color environment. But in general, making a palette full of pmCourteous colors is a lot better than hard-coding RGBColors into your code. Instead of hard-coding colors, make a palette of courteous colors--as many entries as you need colors--and save it as a 'pltt' resource. When your application runs, call SetPalette to attach this palette to your off-screen cGrafPort. When you need to use a color while drawing into this cGrafPort, pass the desired color's palette index to PmForeColor or PmBackColor, and then draw. This is better than hard-coding colors because you or a software localizer can easily change the colors by changing the 'pltt' resource--no code changes are necessary.

The pmWhite and pmBlack usage-mode modifiers are new with System 7; they let you specify whether you want a particular palette entry to map to white or black in a black-and-white graphics environment. By default, colors whose average color-component value is larger than 32767 are mapped to white and other colors are mapped to black. (If you use RGBForeColor, Color QuickDraw also checks to see whether your specified color is different from your background color but maps to your background color; if so, Color QuickDraw uses the complement of the color you specified so that your drawing is visible over the background.) By specifying that a palette entry is pmCourteous + pmBlack or pmCourteous + pmWhite, you can control which colors map to black and to white when there aren't enough colors available. This applies to palettes attached to off-screen cGrafPorts as well as to palettes attached to windows.

Those are the Palette Manager features that do work off-screen. Now I'll talk about the features that don't and what you can do to get the same effect. The pmExplicit usage mode is handy when you want to draw using a pixel value without knowing or caring what color that pixel value represents. With this mode you can easily show the colors in a screen's color table, and you can also draw into a pixel image with a specific value even though you specify the color for that value elsewhere.

When you have a palette that's attached to an off-screen cGrafPort, pmExplicit colors are interpreted as pmCourteous colors. Instead of using a palette, you should convert your pixel value to an RGBColor and use this as the foreground or background color. Set the current GDevice to your off- screen GDevice so that the color environment is set; then pass your pixel value to Index2Color, which is documented on page 141 ofInside Macintosh Volume V. Index2Color converts your pixel value to the corresponding RGBColor, which you can pass to RGBForeColor or RGBBackColor, and then you can draw. The result is that your pixel value is drawn into the destination pixel image.

Both the pmAnimated and pmTolerant usage modes are used to modify the color environment, and both are interpreted as pmCourteous when they're in a palette that's attached to an off-screen cGrafPort. The most important difference between the two usage modes is in the style of color-table arbitration that they do-- pmTolerant gives the front window the colors it needs, while pmAnimated additionally makes sure that nothing outside the front window is drawn in its colors. Color-table arbitration doesn't apply off screen, so the pmAnimated and pmTolerant usage modes can be unified into "I want to change my off-screen colors."

Changing the colors in an off-screen color environment means changing its color table; the most straightforward way to do this is to modify the contents of the color table directly. That is, get your off-screen color table's handle and then directly assign new values to the rgb fields in its CSpecArray. You could also assign a whole new color table to the off-screen environment by assigning the new one to the pmTable field of the off-screen pixMap. Either way, you have to tell Color QuickDraw what you've done by updating the changed color table's ctSeed field. The next time you draw into your off-screen graphics environment, Color QuickDraw detects your change by comparing the ctSeed of your changed color table against the iTabSeed of the current GDevice's inverse table, and it rebuilds the inverse table according to the changed color table. You can update the ctSeed field by assigning to it the return value of GetCTSeed, which is documented on page 143 ofInside Macintosh Volume V. If the 32-Bit QuickDraw extensions are available, you can update a color table's ctSeed simply by passing the color table to CTabChanged, documented on page 17-26 ofInside Macintosh Volume VI.

If you have a GWorld and you want to replace its color table, you should call UpdateGWorld, passing it a new color table. UpdateGWorld makes sure that all the cached parts of a GWorld are properly updated, which is tough to do any other way. If you don't pass any flags to UpdateGWorld, it's within its rights to destroy your existing GWorld's image. But if you pass the clipPix or stretchPix flag, UpdateGWorld is obligated to keep your existing image, and it tries to reproduce the existing image in the new colors as best it can.

To wrap up, you can use the Palette Manager with off-screen graphics environments, but you'll only be able to use the pmCourteous usage mode and the pmWhite and pmBlack usage-mode modifiers. But that's not to cast aspersions on these features, because they can be very handy for both on-screen and off-screen drawing. The pmExplicit, pmTolerant, and pmAnimated usage modes don't work for off-screen drawing, but there are easy ways to simulate those features without the Palette Manager and without risking future compatibility.

FORREST TANAKA has been playing Developer Technical Support as one of the graphics support people for slightly more than two years. "It amazes me still," he says, "that the more you learn about the Macintosh graphics tools, the farther off total understanding seems to be." Outside of DTS, he likes to ride his bike, and uses it to commute the three blocks to his office ("Hey, it's faster than driving the three blocks!"), and he likes to try getting his radio-controlled car to act as if it's actually controlled.*

PRINT HINTS FROM LUKE & ZZ is in hibernation.*

For more details about changing or replacing off-screen color tables, see the October 1991 version of Macintosh Technical Note #120, "Principia Off-Screen Graphics Environments." *

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Adobe Creative Cloud 2.2.0.129 - Access...
Adobe Creative Cloud costs $49.99/month (or less if you're a previous Creative Suite customer). Creative Suite 6 is still available for purchase (without a monthly plan) if you prefer. Introducing... Read more
Tower 2.2.3 - Version control with Git m...
Tower is a powerful Git client for OS X that makes using Git easy and more efficient. Users benefit from its elegant and comprehensive interface and a feature set that lets them enjoy the full power... Read more
Apple Java 2015-001 - For OS X 10.7, 10....
Apple Java for OS X 2015-001 installs the legacy Java 6 runtime for OS X 10.11 El Capitan, OS X 10.10 Yosemite, OS X 10.9 Mavericks, OS X 10.8 Mountain Lion, and OS X 10.7 Lion. This package is... Read more
Adobe Muse CC 2015 2015.0.1 - Design and...
Muse CC 2015 is available as part of Adobe Creative Cloud for as little as $14.99/month (or $9.99/month if you're a previous Muse customer). Muse CS6 is still available for purchase (without a... Read more
Adobe Illustrator CC 2015 19.1.0 - Profe...
Illustrator CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Illustrator customer). Illustrator CS6 is still available for... Read more
Corel Painter 14.1.0.1105 - Digital art...
Corel Painter helps you create astonishing art in a variety of media. Paint with vivid oil paints, fluid water colors, and earthy charcoals. Corel Painter flawlessly recreates the tones and textures... Read more
Pacifist 3.5.4 - Install individual file...
Pacifist opens up .pkg installer packages, .dmg disk images, .zip, .tar. tar.gz, .tar.bz2, .pax, and .xar archives and more, and lets you extract or install individual files out of them. This is... Read more
Merlin Project 3.1.0.40305 - Project man...
Merlin Project is for those of you who are responsible for complex projects. Simple lists of tasks won't suffice. Good planning raises questions about the dependencies of activities on each other,... Read more
DM1 2.0 - Advanced drum machine. (Commer...
DM1 is an advanced Drum Machine. It turns your computer into a fun and creative beat making machine. Easy and fast to use, loaded with 86 superb electronic drum kits and beautiful hyper-realistic... Read more
Posterino 3.2.1 - Create posters, collag...
Posterino offers enhanced customization and flexibility including a variety of new, stylish templates featuring grids of identical or odd-sized image boxes. You can customize the size and shape of... Read more

Mazes of Karradash (Games)
Mazes of Karradash 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The city of Karradash is under attack: the monsters of the Shadow Realms are emerging from the depths.No adventurer is... | Read more »
Battle Golf is the Newest Game from the...
Wrassling was a pretty weird - and equally great - little wressling game. Now the developers, Folmer Kelly and Colin Lane, have turned their attention to a different sport: golfing. This is gonna be weird. [Read more] | Read more »
Qbert Rebooted has the App Store Going...
The weird little orange... whatever... is back, mostly thanks to that movie which shall remain nameless (you know the one). But anyway it's been "rebooted" and now you can play the fancy-looking Qbert Rebooted on iOS devices. [Read more] | Read more »
Giant Monsters Run Amok in The Sandbox...
So The Sandbox has just hit version number 1.99987 (seriously), and it's added a lot more stuff. Just like every other update, really. [Read more] | Read more »
Fish Pond Park (Games)
Fish Pond Park 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: Nurture an idyllic slice of tourist's heaven into the top nature spot of the nation, furnishing it with a variety of... | Read more »
Look after Baby Buddy on your Apple Watc...
Parigami Gold is the new premium version of the match three puzzler that includes Apple Watch support and all new content. You won't simply be sliding tiles around on your wrist, the Apple Watch companion app is an all new mini-game in itself. You'... | Read more »
Swallow all of your opponents as the big...
Eat all of the opposition and become the largest ball in Battle of Balls now available in the App Store and Google Play. Battle of Balls pits you against other opponents in real time and challenges you to eat more balls and grow larger than all of... | Read more »
PAC-MAN Championship Edition DX (Games)
PAC-MAN Championship Edition DX 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: It’s Your World. EAT IT! Get ready for more ghost chain gobbling and frantic action in PAC-MAN® CE-DX! The... | Read more »
incurve (Games)
incurve 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Get ready for 2 different gravities Goal is to hit as many white dots on your way up.When you're touching the screen, the dots have a... | Read more »
Crossy Road has its Own Merch Store Now....
Do you like Crossy Road? I mean do you really like Crossy Road? Well then you're in luck! Hipster Whale has opened up a Crossy Road store, so you can show off your fandom via official T-shirts. [Read more] | Read more »

Price Scanner via MacPrices.net

Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
13-inch 2.5GHz MacBook Pro on sale for $899,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $899.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $200 off MSRP. Price is... Read more
21-inch 2.9GHz iMac on sale for $1299, save $...
Best Buy has the 21″ 2.9GHz iMac on sale today for $1299.99 on their online store. Choose free shipping or free local store pickup (if available). Their price is $200 off MSRP, and it’s the lowest... Read more
Free Image Sizer 1.3 for iOS Offers Photo Edi...
Xi’An, China based G-Power has announced the release of Image Sizer 1.3 for the iPhone, iPad, and iPod touch, an important update to their free photo editing app. Image Sizer’s collection of easy to... Read more
Sale! 13″ 1.6GHz/128GB MacBook Air for $899,...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model. Read more
13-inch Retina MacBook Pros on sale for $100...
Best Buy has 13-inch Retina MacBook Pros on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Prices are for online orders only, in-store... Read more
Will BMW’s i3 Electric Vehicle Be The Automo...
The German-language business journal Manager Magazin’s Michael Freitag reports that Apple and the German performance/luxury automaker Bayerishe Motoren Werke (BMW) are back at far-reaching... Read more
Sale! $250 off 15-inch Retina MacBook Pro, $2...
B&H Photo has lowered their price for the 15″ 2.2GHz Retina MacBook Pro to $1749, or $250 off MSRP. Shipping is free, and B&H charges NY sales tax only. They have the 27″ 3.3GHz 5K iMac on... Read more
Global Smartphone Market Posts 11.6% Year-Ove...
According to the latest preliminary data released from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, smartphone vendors shipped a total of 337.2 million units... Read more
15-inch and 13-inch Retina MacBook Pros on sa...
B&H Photo has 15″ & 13″ Retina MacBook Pros on sale for up to $180 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1819 save $180 - 15″ 2.... Read more

Jobs Board

*Apple* Customer Experience (ACE) Leader - A...
…management to deliver on business objectives Training partner store staff on Apple products, services, and merchandising guidelines Coaching partner store staff on Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
*Apple* TV Product Design Internship (Spring...
…the mechanical design effort associated with creating world-class products with the Apple TV PD Group. Responsibilities will include working closely with manufacturing, Read more
*Apple* Watch SW Application Project Manager...
**Job Summary** The Apple Watch software team is looking for an Application Engineering Project Manager to work on new projects for Apple . The successful candidate Read more
*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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.