Modern Minds, Inc. - ChannelsApplet Applet

hannelsApplet (Version 1.1)

ChannelsApplet is an applet and a canvas class that can be used to program animated transformations of the red, blue, and green channels of a GIF or JPEG image. In addition, the applet can perform vertical and horizontal sine wave distortions on all image channels simultaneously.

A URL (and optionally, a URL target) can also be set for the applet. When the applet area is clicked, the specified URL will loaded in the (optional) designated target.

peration

The following documentation describes how the ChannelsApplet class is used. You can also use the ChannelControl canvas class if you wish to integrate channel animation in your own application or applet. The ChannelControl class is documented separately.

During initialization, ChannelsApplet loads the GIF or JPEG image that will be animated, and an (optional) transparent GIF file that is overlaid after each frame of the animation has been rendered.

In order to animate individual channels of an image, the applet requires you to write an set of animation instructions, hereafter referred to as a program. The animation program can be included in the HTML as a parameters of the APPLET tag, or it can be placed in a text file on the server (i.e., the location from which the Java code is loaded).

Note that it is possible to place an animation program in both locations. In the event that the animation program file cannot be loaded, then the animation program in the HTML will be used. Instructions for creating the animation program as a file will be discussed first, then the procedure for adapting the program to HTML will be described.

Each line of text in the animation program file represents the transformation instructions that should be carried out for a single frame of animation. There are seven different commands available: move red channel (MR), move green channel (MG), move blue channel (MB), move all channels (MA), horizontal wave (H), vertical wave (V), and reset image (R). Each command is detailed below.

CHANNEL MOVE COMMANDS MR (Move Red), MG (Move Green), MB (Move Blue), MA (Move All Channels) Format: [MR | MG | MB | MA] [X Delta (-999 to +999)] [Y Delta (-999 to +999)] Example: "MB-010-010 MG+010+010 MR-010+010 MA+000+010" Explanation: For this frame, a) Move blue channel up 10 and left 10, then b) Move green channel down 10 and right 10, then c) Move red channel up 10 and right 10, then d) Move all channels down 10. NOTE: The X and Y offsets are always from the position of the original image, NOT from the position of the image in the preceding frame! IMAGE RESET COMMAND Format: [R] [Percent (000 - 100)] Example: "MA+50-35 R050" Explanation: For this frame, a) Move all channels (i.e., move image) down 50 and left 35, then b) Reset image for next frame's transformation to 50% of this frame after transformation and 50% of original image. NOTE: R100 would reset the image for the next frame to the original image. This is the default behavior if no reset command is specified, so R100 would be redundant. Also, remember that the Reset command ONLY EFFECTS THE NEXT FRAME, not the current frame. IMAGE WAVE COMMANDS V (Vertical Wave), H (Horizontal Wave) Format: [V | H] [Number of Waves (1 - 9)] [Percent (000 - 100)] [Offset Degrees (000 - 360)] Example: "MG+010-010 V1004000 H1002000 R080" Explanation: For this frame, a) Move green channel down 10 and left 10, then b) Perform a vertical wave transformation on the image with one sine wave having a maximum modulation of 4% of the image height and with the waveform beginning at an offset of 0 degrees, then c) Perform a horizontal wave transformation on the image with one sine wave having a maximum modulation of 2% of the image height and with the waveform beginning at an offset of 0 degrees, then d) Reset image for next frame's transformation to 20% of this frame after transformation and 80% of original image.

In addition to these standard commands, ChannelsApplet supports one special command. If you wish to repeat a frame without applying any transformations, you may enter the command STATIC on a single line. This will cause the previously rendered frame to be repeated in the animation sequence.

The last line in the animation program file should be a line with the instruction END on it. This instruction tells ChannelsApplet to stop reading the file for animation instructions. The END instruction is not necessary if the animation program is in the HTML.

To place the animation program within the APPLET tag in the HTML, a frames parameter must be specified that contains the total number of frames to be generated for the animation. A series of frameNN parameters must also be specified, each of which contains the animation instructions for the particular frame.

For example, if there are instructions for three frames of animation, then the parameters would look like:

<PARAM NAME="frames" VALUE="3"> <PARAM NAME="frame1" VALUE="V1004005 H1002000 MG-005+005"> <PARAM NAME="frame2" VALUE="V1004000 H1002005 MG-005+010"> <PARAM NAME="frame3" VALUE="MG+005-005 V1004000">

ample

If your browser supports Java, you should see a demonstration of the ChannelsApplet to the left of this text.

You can view the program instructions that produced this animation.

arameters

Following are the HTML parameters for the applet. A parameter marked "Opt" is optional, and a parameter marked "Req" is required.

Req	image	The file name of the GIF or JPEG image that is to be animated. The file path is based starting with the directory in which the Java applet is located.
Opt	mask	The file name of a transparent GIF (GIF89a format) image that will be drawn on top of each rendered frame. (The animated image is overlaid with the non-animated mask image.) The file path is based starting with the directory in which the Java applet is located.
Opt	initWithImage	If set to "true", then the applet will draw the original image and then the mask overlay (if specified) before the frame rendering process begins. This prevents having a blank "hole" while the rendering process is executing. If set to "false", then only a progress bar at the bottom of the applet will be displayed. If this parameter is not specified, then the parameter value defaults to "false".
Opt	frameDelay	The number of milliseconds to delay between each frame of animation
Opt	loopDelay	The number of milliseconds to delay between each animation loop.
Opt	direction	The sequence in which the frames of animation are displayed. If set to "forward", then the animation is displayed beginning with frame one, and ending with the last frame. If set to "backward", then the animation is displayed beginning with the last frame, and ending with the first frame. If set to "yoyo", then the animation is alternated between "forward" and "backward". If this parameter is not specified, then the parameter value defaults to "yoyo".
Opt	background	The background color used during the rendering process. The color specified for this parameter can have a substantial affect on a rendered frame. The value must be a hexadecimal RGB value. If instance "FF0000" would be red, and "888888" would be a medium gray. The color defaults to black if not specified.
Opt	networkFile	The file name of the text file that contains the animation program (i.e., the rendering instructions for each frame of animation). If the file cannot be opened, then the applet will try to use the animation instructions defined in the frameNN parameters (see below), if they have been specified. The file *must* reside in the same directory as the Java applet.
Opt	frames	The number of frames of animation to be rendered. There must be one frameNN parameter (see below) for each animation frame. This parameter is read only if the networkFile parameter is not specified, or if the applet cannot open the specified networkFile.
Opt	frameNN	The rendering instructions for each frame of animation. There must be one frameNN parameter for each frame of animation as specified in the frames parameter (see above). For example, if the frames parameter is set to 3, then there must be a frame1, frame2, and frame3 parameter. See the Operation section of this documentation above for information regarding the format of the rendering instructions.
Opt	appletBG	This parameter is used to set the applet's background color. The applet background color can sometimes be seen during a screen refresh when the page that contains the applet is scrolled or resized (do not confuse the applet background color with the background color used for the animation). The `appletBG` parameter has been provided to allow you to set the applet background color so that the applet refresh is not as noticeable when the page that contains the applet is scrolled or resized. If a value for this parameter is specified, then the value must be a hexadecimal RGB value. For instance "FF0000" would result in a red applet background, and "888888" would result in a medium gray applet background (visible only during a screen refresh). If this parameter is not specified, then the applet background color will default to the browser background color.
Opt	url	This parameter specifies a URL to load when the mouse is clicked within the applet area.
Opt	target	This parameter specifies an optional target for the url parameter.

xample

An example of a HTML APPLET tag with all parameters for this applet is shown below. Note that image and mask images should be the same size, and that the image dimensions are used for the applet width and height parameters.

ownload

The applet ChannelsApplet, along with a copy of this documentation, is available for download as a standard zip file, as a self-extracting file (for Windows95/NT users), or as a self-installing Java class file.

opyright

This documentation and the object code for ChannelsApplet and ChannelControl may be copied and distributed freely for non-commercial purposes so long as neither the code nor the documentation is altered in any way. If the object code is distributed with any documentation whatsoever, then this unaltered document must accompany the code.

Copyright © 1997, 1998 by Modern Minds, Inc.