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Making Jpeg Previews
version 2.12
Please note the "usenethelp@codeccorner.com" address above. This primer will be relocating there during the summer.


Why Make Previews?

by PolarBear and hld3 by Methos
Capturing A Still Image - Simple Tools Individual screen shots
Making A Contact Sheet Create a contact sheet.
Getting Fancy - More Software Tools
Making Previews with *nix by Harvey W
A Word About Text Captions
Finally...



Why Make Previews?

And LO! It was written in the ABME VFAQ's:

"09. ALWAYS provide a preview, whether a new cap or a repost. Either a jpg still or a text message in the 00 part. It will cut down on the messages to answer."

That's one good reason. Here's another. A good cap deserves a good preview. Capturing and editing a clip involves a certain amount of work, and a preview provides the finishing touch, the final polish. It also makes it more likely that your cap will be seen and saved by downloaders - that is, after all, why you're posting it in the first place.

There's an old saw that a picture is worth a thousand words. Does this mean that 100 pictures are worth one hundred thousand words? Probably not. When making previews, there is the question of how many images to include. A judgement call, really. A single, good image can be enough of a preview to cause someone to want to download your cap, and a single, poor image can convince them that as a capper, your stuff isn't worth bothering with. Looking at the previews posted by many cappers over the last few years, the most interesting preview sets usually contain at least six (6) images per clip. These may be uploaded on a single contact sheet, or may be included as a set of single images in a zip file. Looking at past postings, only a few of the most experienced posters have had the "eye" to compose or choose a single still image that reflects their cap.




Capturing A Still Image - Simple Tools

There are several ways of capturing still images from multimedia files. Not all methods work with all types of multimedia codecs and hardware combinations; it's usually a matter of experimenting a bit.



EXAMPLE 1. This is the most basic type of still image capture, and like most Microsoft features, it doesn't always work - sometimes the "snapshot" will just be a black square. Other disadvantages of this type of still capture are that:
  1. You can wind up with a picture of something other than what you intend, 
  2. the output image is a .bmp file, while .jpgs are preferred, and 
  3. The picture will have a "Windoze" frame around it.
EXAMPLE 2. For some people, the still captured in Example 1 will be sufficient for a preview - that's individual choice. However, if you want to present something a little more "finished-looking", the next step is to crop the image. You can do this using the built in "Paint" program in Windows, using Photoshop, or Graphic Workshop, or any of several other photo/image tools that have a "crop" feature. Most cropping tools are easy to use - just "click", "drag", "select", and "save". TIP: Always save your cropped image as a NEW filename. That way, if you make a mess of it, you still have the original image to start again.

When cropping a picture, there are a couple of things to consider. 

  1. The finished size of the image. If you're making a contact sheet, it looks better if the images are more-or-less uniform. 
  2. Any glitches or artifacts around the edges of the image. Stills capped from VHS, in particular, often have a motion bar across the bottom. At this stage, it's easy to clean that up. 
  3. What else is in the picture? If there's one person you want to highlight, you may want to trim off the surrounding parts of the image.

 
 



Making A Contact Sheet
Once you have your images selected and prepared, a further step is to make them into a contact sheet. There are several methods of doing this, some easy, some more time-consuming. Using programs like Adobe Photoshop, it is possible to manually lay out a contact sheet of multiple preview images by opening and pasting the individual preview jpgs into a new master image. The same job can be done in MS-Paint, but frankly "Paint" is not suited for this type of work, and trying to lay out a contact sheet with it is a real pain in the butt.

The easiest and quickest method, and one that gives good control over the result is to use the "Thumbnail", "Catalog", "Contact Sheet", etc. features of programs like Graphic Workshop Professional and LView Pro. Many of these programs are available as Shareware; check Tucows for new additions. In these programs, all you have to do is select the select the image size, choose the images to go on the page, and "Go".

One nice feature about both LView Pro and Graphic Workshop is that they can re-size your source images as they are placed on the contact sheet, making them all nice and uniform. You can also change the position of the images, and add caption text as needed. In addition, you can add borders to the images, and choose a variety of background presentations. Some simple examples:

Some Simple Examples
Click On Any Image To See Full-Size Version

Getting Fancy - More Software Tools

Although tools like LView Pro and Graphic Workshop make the task of composing contact sheets a snap, they don't do too anything about reducing the "donkey work" that goes with capturing stills from a video clip. True, a good capturing tool, like Hypersnap, makes the job much easier, but it's still a manual process. For those using .avi codecs there is an "automated" alternative.

I came across this software while looking for an answer to the following: I had said to myself, "Self, wouldn't it be handy if, instead of playing each avi cap in Virtual Dub, and pressing [CTRL-2] and [PASTE] repeatedly, there was a little program that would play the avi, and grab a frame every so many frames, or so many seconds, then write it as a sequentially-numbered thumbnail?" "Or better yet, dump them all on a contact sheet?" "Yup!" And there is.

Smaller Animals Thumbnailer will play a video clip, in any one of several formats including various avi codecs, and spit out thumbnails. Not just at random, either. It will generate thumbnails every "N" frames, every "N" seconds, or else generate "N" thumbnails per clip. The size of the output thumbnails is configurable, and if the desired size is different than the clip format size, it will fill in the blank space with a selectable matte colour.

Other tools built in to S.A. Thumbnailer include contact-sheet creation, thumbnail creation from a catalogue of images, text overprinting, logo overprinting, image format conversion and resizing. There is also a limited capability for levels manipulation and cleanup. The package includes a variety of tools for web page production; these are not of interest in creating preview jpgs for ABME, but may be useful for other things.

To make previews with S.A. Thumbnailer, here's a quick outline of the procedure:

Using Smaller Animals Thumbnailer on the auto-capture setting, capture "n" (usually 15 or 20) still images from each .avi file to a temp directory. (SA Thumbnailer will not capture still images from mpegs). Thumbnailer auto-names these by clip name. Be sure the "Write Thumbnails" checkbox under "Advanced Settings/General Operation" is checked.
Manually view these using a jpeg viewer (ACDSee), and toss out those that are badly composed, end-of-scene, etc. Then toss out those that are "dupes" or visually similar.
Reset the controls on SA Thumbnailer to use its "Composite Image" feature. This does the same job as Graphic Workshop - creates a matrix or contact sheet from individual still images. Unfortunately, Thumbnailer doesn't read its own filenames very well, so separate the captured stills into separate directories ("A", "B", "C", etc., to avoid crossovers) if you're making previews for more than one clip.
Select the input directory - where you've saved the stills from your auto-capture.
Set the output directory to whatever you want.
Set the size of the thumbnails to something reasonable, like 240x180 or 180x120. Thumbnailer will adjust the size of the finished image. Remember that a typical format for an ABME-posted clip is 320x240 or 352x240 - so you want a thumbnail smaller than that, but not so small that nothing can be seen.
Select the "output matix" you want to use. 3x2 will give 6 images per page; 3x3 will give 9 images per page, and so on. Anything more than 12 and things get pretty squashed.
Be sure the "Write Thumbnails" checkbox under "Advanced Settings/General Operation" is checked when auto-capturing, and UN-checked when making contact sheets!
SA Thumbnailer can automatically add some captioning information across the top of a composite image - this is quite a nuisance to set up, but works well once it is configured. There is info in the "help" file on this - basically you can either type the data into the program each time, or have it refer to an outside file called "caption.txt" which you edit for each cap. Font size, typeface, and colour are fully configurable.
If you don't want to mess around with this "feature", it's probably just as quick to add text using an image-editing program like Photoshop.
If you want to add additional text captioning, logos, "pretty them up", etc. use Photoshop, etc.
 
Basic 6-image contact sheet made with S.A. Thumbnailer. Clip and codec information is included in caption applied with Thumbnailer program. Plain font in contrasting colour is used with a dark background. 
Basic 12-image contact sheet made with S.A. Thumbnailer. Clip and codec information is included in caption applied with Thumbnailer program. Plain font in contrasting colour is used with a dark background. 
A little fancier. 12-image contact sheet, made with S.A. Thumbnailer. Clip and codec information is included in caption applied with Thumbnailer. A more elaborate font was used - but it's less readable. The "Polar Bear" logo at the bottom was added with Adobe Photoshop. 
A joke "preview" created completely with Adobe Photoshop, using random stills downloaded from the 'Net. A much wider range of text, colour and graphic options are available. But it's a lot more work. 
A basic 4-frame preview for a ZealandMan cap. Images were captured from mpeg files using the "Copy Source Frame" command in VirtualDub, and saved. These were then imported into Adobe Photoshop and placed on a background. Text and logo were also added with Photoshop. [Naughty bits edited for the web] 


Step-by-step guide to producing simple contact sheets

Step 1 - Produce individual screen shots

In Animation Shop 3 (Comes with JASC Paint Shop Pro 7)

1. File->Open
2. Select your video file (AVI or MPEG)
3. click Open. After a few seconds, you should get a dialog displayed 'Video Import Options'
4. In the 'Sampling' group, click 'Take one sample for every' and enter a number to give you as many frames as you wish. e.g. If you have 7000 frames listed in the 'Range of Frames to import' group on the same dialog) and you wish 99* (see later) screen grabs, enter 71
5.Press OK. The next part may take from a few seconds to a few minutes depending on the size of the video file. When complete, you will have a 'strip' of images.
6. Highlight the first image and press Ctrl-A (or Edit->Select All)
7. Save the images, preferably in their own folder using File->Save Frames As... (not Save As...)
Now we'll see why I chose 99 screen grabs. Animation Shop 3 will append a number on to each image name and save it as a separate file, but it won't zero pad them, so you'll end up with Image 1.jpg, Image2.jpg ... Image 10.jpg etc. When viewed in a folder (and later in the preview generator) you'll find the order incorrect (1,10,11..19,2,20 etc) I then rename the 1-9 images to 01-09 to correct this.


Step 2 - Create a simple contact sheet.

Open one of the images in Irfanview and

1. select 'Thumbnails' File->Thumbnails. A thumbnail page will now open list all of the images in the same folder.
2. Preview the images you wish (dbl click) and discard those you don't want (del). DO NOT close the preview image window as this is used to create the Contact Sheet. I usually remove enough images to leave a good preview (up to 49 images left, but that's up to you)
3. Select the remaining images (draw a box around them, or use standard ctrl and shift mouse clicks)
4. In the Thumbnail widow:
a. File->Create contact sheet from selected thumbs...
These are examples I've done:
Width: 1280
Height 1024 (resolution)
Columns: 7
Rows: 7 (for 49 images)
Spacing - H: 15
Spacing - V: 10
Margin - H: 15
Margin - V: 30
BG color: Black
Font: 20pt
Write Filenames: Unchecked
Headnote: Test Contact sheet
Footnote: Ripped by Methos
b. Click Create.
You can repeat this until you get the correct look and then on the image window:
5. File-> Save As. Choose jpg and set you own compression
6. And you should end up with:

Making Previews with *nix by Harvey W
Making previews on *nix-like systems with xine (http://xine.sf.net) and imagemagick (both FREE) (http://imagemagick.sf.net) is dead easy:
1) play the movie with xine - % xine <filename>
2) use xine's "snapshot" function (click on the camera button or use the 't'-key) to capture as many frames as you like
3) use montage (part of ImageMagick) to combine the individual frames - % montage <snapshot files> <preview>
hints:
    o use the 0-9 keys to quickly jump to the start, 10, 20, ... 90% of the   file with xine
    o if you have trouble finding the snapshot images, note that xine puts them in your home directory
    o add text to the preview with montage's "-title" option - % montage -title "file.avi\n(100 megs, 320x200)" xinesnap* preview.jpg



A Word About Text Captions
If you're making a preview contact sheet for a video clip, it's useful to put certain information on the image, since a) many downloaders don't save posted "0" files, and b) it helps identify your clips later on. At a minimum, include the name of the clip and how many parts it has. If you know them, the performer name(s) are good. The video codec you've used to make the cap is also a Really Good Thing. Overall size in Megabytes, and running time of the clip are handy, if you have room. Finally, the nym of you, the capper, lets people know who's responsible for your masterpiece(!).

Sometimes, it's not easy to add all this in text to a contact sheet. An alternate method of including the information is to make a single frame still with all the info (remember to make it the same size as the still frames on your contact sheet - MS Paint works well for this) and just plonk it in as the first or last frame on each contact sheet - whatever is quickest.

It's a good idea to use PLAIN, READABLE fonts, and viewable colours that don't bleed. Deathwatch-Goth font in Electric-Blue text on a Violent Violet background may be your idea of a nifty graphic look, but it's not so great if nobody can read it. Remember that the idea is to supply information about your cap.


Finally...
Making previews is not, for the most part, very difficult. Depending on the methods you use, and how elaborate you want to make them, it can be time consuming. By using software tools to eliminate some of the more labour-intensive parts of the job, it can be made quite a bit easier. Even a modest set of previews - a few stills - can tip the balance when people are deciding whether or not to try and download your caps. This is especially true for those downloaders who are using modem connections.

Since you've gone to all the trouble of making those killer caps, why not finish them off with some killer previews?



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