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

VueScan 9.5.70 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
TextSoap 8.3.2 - Automate tedious text d...
TextSoap can automatically remove unwanted characters, fix up messed up carriage returns, and do pretty much anything else that we can think of to text. Save time and effort. Be more productive. Stop... Read more
ForkLift 3.0 - Powerful file manager: FT...
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
Amazon Chime 4.0.5528 - Amazon-based com...
Amazon Chime is a communications service that transforms online meetings with a secure, easy-to-use application that you can trust. Amazon Chime works seamlessly across your devices so that you can... Read more
Sparkle 2.1.0 - $79.99
Sparkle will change your mind if you thought building websites wasn't for you. Sparkle is the intuitive site builder that lets you create sites for your online portfolio, team or band pages, or... Read more
Bookends 12.7.9 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Dash 4.0.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
TrailRunner 3.8.834 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more
Dash 4.0.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Bookends 12.7.9 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more

Fantasy MMORPG MU Origin’s receives a hu...
Developer Webzen are looking to take their highly popular fantasy battler MU Origin to the next level this month, with its most ambitious overhaul yet. The latest update introduces the long sought after Server Arena, new treasure dungeons, and much... | Read more »
RPG Djinn Caster (Games)
RPG Djinn Caster 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: SPECIAL PRICE 38% OFF(USD 7.99 -> USD 4.99)!!!A Fantasy Action RPG of far foreign lands! Summon the Djinns and rise to... | Read more »
Alto's Odyssey gets its first trail...
There's finally video evidence of Alto's Odyssey, the follow up to the 2015 App Store hit, Alto's Adventure. It looks just as soothing and atmospheric as Alto's last outing, but this time players will be journeying to the desert. Whereas Alto's... | Read more »
Last week on Pocket Gamer
What’s going on in the wider world of portable gaming? Each week we ask that question of our sister website Pocket Gamer. The PG team covers iOS gaming, just like 148Apps, but it also strays into the world of Android games and handheld consoles... | Read more »
Pokémon GO Generation 2 evolution guide
At long last, Niantic Labs finally unleashed the Generation 2 Pokémon into the wild. Pokémon GO trainers are scrambling to grab up this new set of 80 Pokémon. There are some special new tricks required to catch all of these new beasties, though.... | Read more »
The best new games we played this week
It feels as though the New Year got off to a creaking start as far as mobile games go, but that's changed over the past few weeks. The last few days alone have seen the debut of a number of wonderful games, so we thought we'd take the time to... | Read more »
Recruit more scallywags and discover new...
Get ready to show off your sea legs all over again in Oceans & Empires’ new grand update, which aims to make the act of rising to the role of seven seas ruler even more fresh and appealing, thanks to a richness of new content on both iOS and... | Read more »
Mage the Ascension: Refuge (Games)
Mage the Ascension: Refuge 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: The groundbreaking roleplaying game Mage: The Ascension manifests in our turbulent present with Refuge, an... | Read more »
Vampire: Prelude (Games)
Vampire: Prelude 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: The classic roleplaying game Vampire: The Masquerade returns to digital games with a Prelude of things to come. Experience a... | Read more »
Digby Forever Guide: How to dig to the d...
Digby Forever is a sparkling homage to arcade classics, and while you may be tiring of the number of arcade games being thrown at you, this endless digger finds many ways to stand out from the rest of the pack. The game manages to be challenging... | Read more »

Price Scanner via MacPrices.net

Apple Certified Refurbished iMacs available f...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Apple offering Certified Refurbished Series 1...
Apple is now offering Certified Refurbished Series 1 and Series 2 Apple Watches for 14-16% off MSRP, starting at $229. An Apple one-year warranty is included with each watch. Shipping is free: Series... Read more
1.4GHz Mac mini on sale for $449, save $50
B&H Photo has the 1.4GHz Mac mini on sale for $50 off MSRP including free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP Read more
12-inch Retina MacBooks on sale for $200-$250...
Newegg has the 12″ 1.2GHz Space Gray Retina MacBook (sku MLH82LL/A) on sale for $1349.99 including free shipping. Their price is $250 off MSRP, and it’s the lowest price available for this model.... Read more
13-inch 2.0GHz Space Gray MacBook Pro on sale...
Adorama has the non-Touch Bar 13″ 2.0GHz Space Gray MacBook Pro in stock today for $100 off MSRP. Shipping is free, and Adorama charges NY & NJ sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray... Read more
13-inch Touch Bar MacBook Pros on sale for $1...
B&H Photo has select 2016 Apple 13″ Touch Bar MacBook Pros in stock today and up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar MacBook... Read more
KSI-1802R SX Disinfect-able Keyboard With Wav...
KSI has unveiled a new, innovative medical keyboard, the KSI-1802R SX, at HIMSS 2017, running February 19-22 in Orlando, Florida. KSI-1802R SX is the only keyboard that combines dual factor... Read more
15-inch Touch Bar MacBook Pros on sale for up...
Amazon has 15″ Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP including free shipping: - 15″ 2.7GHz Touch Bar MacBook Pro Space Gray: $2720.38 $79 off MSRP - 15″ 2.7GHz... Read more
Apple’s Education discount saves up to $300 o...
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: -... Read more
13-inch 1.6GHz/256GB MacBook Air on sale for...
Newegg has the 13″ 1.6GHz/256GB MacBook Air (MMGG2LL/A) on sale for $1029.99 including free shipping. Their price is $170 off MSRP, and it’s the lowest price available for this model. Choose Newegg... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Manager *Apple* Systems Administration - Pu...
Req ID 3315BR Position Title Manager, Apple Systems Administration Job Description The Manager of Apple Systems Administration oversees the administration and Read more
*Apple* Technician - nfrastructure (United S...
Let’s Work Together Apple Technician This position is based in Portland, ME Life at nfrastructure At nfrastructure, we understand that our success results from our Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Manager *Apple* Systems Administration - Pu...
Req ID 3315BR Position Title Manager, Apple Systems Administration Job Description The Manager of Apple Systems Administration oversees the administration and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.