Personal Paint offers a unique range of features designed for authors of artwork to be distributed on computer files. In this document, we would like to share with you some of the experience collected by leading artists. We also explain some of the settings we at Cloanto prefer in our own configurations. The section references are relative to the documentation of Personal Paint 7.
An image or an animation created with public distribution in mind requires some considerations which are normally not relevant when a file is used only on the author's computer.
As the public grows wider, compatibility becomes an issue: the image or the animation may have been created using a screen mode different than what a viewer may have available. Some (especially older) picture and animation players had limitations and bugs, and it could be interesting to have access to a range of options designed to prevent potential difficulties before they become a problem for end users.
Associating information such as author, copyright, and other comments to files is usually appreciated both by authors and by the public (as well as by possible publishers). Also, there should be no difficulties or formalities in distributing the icons created by the art application, or even replacing these with new default icons. Both the icons and the image file should be product-neutral (no hidden advertising texts inside the file). After more than six major versions, Personal Paint offers experienced answers to these and many more requirements.
Most computing platforms use display modes made of square pixels (i.e. an X/Y ratio of 1, as on the original Macintosh hardware, or on the PC's VGA and derived display modes) as a standard. This means that the pixels are exactly as tall as they are wide. To be round, a circle drawn on such a screen would be as wide (in pixels) as it is tall. Not so on the Amiga. The original non-interlaced Amiga modes had a ratio close to 0.5 (so-called "tall-pixels"). A "round" circle could be 10 pixels on the X-axis and 5 pixels on the Y-axis. Most artists prefer to work with square pixels. Yet even here there is no exact match on the Amiga. PAL and NTSC screen modes, for example, have pixels of slightly different ratios. Before it draws a circle, Personal Paint queries the Amiga Display Database to obtain information on the ratio. For example, the Display Database could tell Personal Paint that a "round" circle must be 10 pixels wide and... 9 pixels tall. This is not what most artists want. Rather than working with similar approximations, at Cloanto we prefer to activate the Square Pixels option (section 9.13.5 of the manual). This ensures that the resulting images appear correctly when viewed using 1:1 pixels, regardless of the screen mode in which the image was created.
Normally, when storing an image in formats such as IFF-ILBM, information about the current screen mode is also saved. When the Amiga was first released, associating a screen mode to an image allowed simple viewer applications to quickly open a screen of the same type as the one used by the author. At that time, options were limited: screens could be either low resolution or high resolution, interlaced or non-interlaced. These were common to all Amigas. Minor difficulties would result from images crossing the oceans separating PAL from NTSC video modes. Today, there are not only different generations of Amiga display hardware, but even third-party graphics boards. Even users of identical Amiga computers may have installed different Monitor files on their systems (section 11.4). Furthermore, applications became more intelligent: Personal Paint, for example, excels in automatically picking the best available screen mode to display an image.
Over the years, associating default screen modes to pictures has become more dangerous (the default may not be available, or viewable, on the user's machine) and less necessary (software is more intelligent). At Cloanto, we now prefer to store all images without associating a default screen mode to the file. To switch this option, open the Options window in the Save Image requester (section 4.2) and clear the Screen Format setting. File formats which cannot save screen mode information (e.g. PBM) do not have this option.
Animations require some additional attention. In accordance with the different Amiga ANIM specifications (standards for animation file formats), a default screen mode must be specified in the file. Personal Paint and the most used Amiga animation players are capable of overriding this information when loading an animation, and can automatically select an appropriate screen mode just as Personal Paint does for images. This is necessary, for example, when an animation's default mode is not supported on the computer where the animation is to be played. Nevertheless, when an animation is saved, the current screen mode is always stored with the animation. At Cloanto, we have decided to associate "DblPAL" screen modes to the animations we create and distribute. These screen modes are supported by all AGA machines, and can be displayed on VGA monitors not supporting 15 kHz modes. Furthermore, the pixel X/Y ratio of PAL is closer than NTSC to 1, which is preferred by most artists. The AGA chip-set is very common among the more active Amiga users. Yet even if the end user's machine does not support DblPAL, the animation can be displayed in other screen modes (the screen mode information is only a hint required by the ANIM standard, not an imperative for applications).
Users of original and ECS Amiga chip-sets, as well as users of some display cards such as the Picasso II should consider another issue: color resolution. AGA allows users and applications to define and set colors using 8 bits per color component (red, green and blue). This is 24 bits (or 256 gray-levels, or more than 16 million different color-combinations). Older Amigas only support 4 bits per component (i.e. 16 gray-levels, or 4096 colors). The Picasso II uses 6 bits per component (64 gray levels, or 262 144 colors). This means that on some systems colors cannot be defined with the precision possible on AGA (e.g. on the Amiga 1200 and 4000), for example. Users of Personal Paint can quickly check the color resolution of a given screen mode by displaying the Palette requester (section 8.1.3) and setting any color-slider to the maximum. The numerical value indicates the precision of the display (e.g. a maximum level of 15, 63 or 255 would indicate that the hardware supports 16, 64 or 256 levels for that color component).
When a palette is loaded on a system with a lower color resolution, a majority of colors is likely to "snap" to coarser levels. If the image is then saved again, a loss of data may occur. As an artist, you may want to make sure that the colors you see on your system will be loaded and represented the same way by an older Amiga. Or, even if you do not own a system capable of handling 8 bits per color component, you may need to edit images in that resolution without losing precision. Personal Paint offers a solution to all these requirements, by allowing the user to manually set the color precision (number of bits per color component). Even if this is different (higher or lower) than what is supported by the system, Personal Paint can use a custom value for all processing, overriding the Amiga defaults. As explained in section C.3, when the program settings REDBITS, GREENBITS and BLUEBITS are set to 0, Personal Paint uses the maximum color resolution supported by the video device currently used. This is the program's default. Other values, however, force Personal Paint to use specific numbers of bits per color component. For example, setting all three values to 8 allows for precise editing of AGA-resolution palettes even on ECS or Picasso II systems.
At Cloanto, where we work with different Amiga computers and graphic boards, we manually set REDBITS, GREENBITS and BLUEBITS to 8 in our own startup files. If you have an AGA computer and you only work in AGA screen modes, you should not need to set these values yourself (by default this is taken care of by Personal Paint), unless you want to emulate a coarser color resolution.
When we save an image, at Cloanto we use the IFF-ILBM format if the image is mainly for Amiga distribution. The options we normally set are: compression active, no screen format information. IFF-ILBM is the most supported Amiga image file format, and also offers excellent loading and saving times (e.g. viewers are faster), but its compression is not as good as in other formats (i.e. the files are longer). When space is really tight and excellent compression is a priority, we use PNG (options: compression level 9, no progressive display, automatic mode enabled). Setting a PNG compression level higher than 6 slightly improves compression, but considerably slows down the compression procedure. PNG is also our format of choice when the images are to be read by other computers. We used to prefer GIF for cross-platform distribution, but GIF's popularity was suffocated at the end of 1994, after Unisys Corporation began demanding royalties for software reading and writing GIF (and TIFF/LZW) files. When we write images to be used on an Amiga CD-ROM, we sometimes prefer another format: uncompressed IFF-ILBM (no compression, no screen format information). This can generate quite long files, but on a CD-ROM space is usually not a problem. Due to the minimum software overhead, uncompressed IFF-ILBM files can be loaded considerably faster than other formats, especially on slower machines.
When we write animations, at Cloanto we usually store them in ANIM-5 format. This is the most supported standard for Amiga animation files. It also offers good compression. ANIM-7 files can be processed faster, although they are not compressed as well and are not as widely supported as ANIM-5. We use ANIM-7 for 256-color animations, and sometimes to store all types of animations on CD-ROM, when we know that an ANIM-7 viewer is available (e.g. Personal Paint). Very rarely, when a disk is really packed, we store animations in the ANIM-5+7 format. When this format is used, Personal Paint decides whether to use ANIM-5 or ANIM-7 on a frame-by-frame basis, depending on which format yields the best compression. This adheres to the ANIM specifications, but requires that the software loading the animation can handle both ANIM-5 and ANIM-7. We never use ANIM-8. It is neither as popular nor (in general) as good as ANIM-7.
Quite often, at Cloanto we use Personal Paint to optimize old animations (use of the Optimize Frames command is explained in section 6.3) before saving them again. This alone can halve the size of certain animation files. Some older and not very popular animation viewers do not support frame-by-frame timing. In this case, the Optimize Frames command cannot be used. These same programs usually also do not support more than one color palette per animation (see the introduction to chapter 6). Personal Paint marks these palettes with three dots under the associated frame in the storyboard (section 6.4). At Cloanto, we use frame-by-frame timing and multiple palettes without concerns, since neither of the limitations described here is an issue with the most recent and the most used Amiga animation viewers.
A few other options can affect the animation format. Before the animation is saved, we make sure that the current screen mode is the one that we want to associate to the animation (see explanation in this same section).
Some older programs have a bug which does not allow them to handle certain types of properly written ANIM files. DPaint (up to release V) is one of these programs. When compatibility with these applications is important, we disable the Full ANIM Optimization option (section 6.2).
As an author or publisher of an image or animation, you may want to fill-in the Author, Copyright and Annotation texts, which are supported by most file formats (section 4.10.1). You could put your name as the Author, and something like "Copyright © [Year of first publication] [Your name] - Freely Distributable" in the Copyright text. The Annotation could include a postal or E-mail address. Personal Paint allows for this information to be easily edited at any time. Empty fields are not saved, and do not occupy any space in the file.
On the Amiga, Workbench icons are usually associated to files. Personal Paints can save images and animations using the default icons stored in the "PPaint:PPaint_Icons" drawer. These icons also determine the Default Tool, which is the program which will be loaded when the file is double-clicked on. If you like the icons which come with Personal Paint (they are freely distributable), you can leave them as they are, or perhaps you may want to change the default tool, for example by putting "VT" instead of "PPaint:PPView". This can be set with the Workbench Information command. PPView is a short program which uses Personal Paint as a viewer (it loads Personal Paint, if it is not already loaded). Please be careful not to Snapshot (Workbench command) the icons inside "PPaint:PPaint_Icons" to a fixed position. When dropping a new default icon inside the drawer, select the Workbench UnSnapshot command.
At Cloanto, we usually set the Icons option to Original (section 9.10.5) when we only want to change the file format of a picture or animation. This guarantees that the existing icon image will not be affected.