Graphics and Still Images John H. Krantz Hanover College

Outline Graphics –Types –Developing with Paint Images –File Types –Acquiring –Using ImageJ Basics Advanced

Graphics vs. Images Some definitions: mine for clarity here: –Graphics Def: computer generated or drawn by you. –Image: scanned, captured, take photograph or an graphic file not generated by you. –Difference: In a graphic, you can directly manipulate the elements because you drew them – Sprites In an image, you can manipulate pixels but not directly the elements. This has a great impact.

Graphic Types Storing Formats: –Bitmap (bmp, PCT, Tiff) – big, not good for web –Compressed Graphic Interchange Format (Gif) can animate –8 bits of color – palette – no spatial compression –Can be some legal issues – make sure the generator legally can generate GIF’s –Generally best compression for simple graphics –Can generate transparent regions JPG –Generally better for images and photos –Spatial not color compression, can distort image spatially. –Now can animate as well.

Developing with ImageJ Free Very simple but easy Access to pixels No anti-aliasing –Downside: jaggies –Upside: in complete control of graphics Can store in Lots of Formats

Try some Basic Graphics Objects Cutting and Pasting –Transparency Adding Text Saving in Different Format –Transparency (set in web page program). Reading Different Formats

Image Types Same as with graphics JPG is generally better in terms of compression ratio, smaller files, for images For complex images, minor spatial distortions will be hidden.

Example JPG

Acquiring Scanning –Flatbed gives best quality. –Use 35 MM film for pictures – best resolution –Scan at a high level and sample down later –Any model seems good this day.

Scanned Image

Digital Cameras No loss in Scanning CCD 3.1 Megapixel at least if need photo quality –there are 5 megapixel –Can use lower quality if only need web. Easy to download Good in low light

Low Light Digital Image

Taking Photos Digitally Focusing: Automatic and Manual –Regular focus –Macro – allows focusing up close –Spot Focus: focus is determined by point Shutter Speed Zoom: –Do not use digital zoom – if need more zoom, do it on computer later –On my default is off except for movies

Taking Pictures (cont.) White Balance, controls for our color constancyWhite Balance, controls for our color constancy –Effect of the IlluminantEffect of the Illuminant Flash: –often I keep it off. Image Size: –I keep at standard (full pixel density, some JPG compression). Balance between image quality and ability to store on disk ~ 1 Meg/picture

Use of Flash FlashNo Flash

Editing Images with ImageJ Free at: Overview –Java program –Interface a bit awkward because not free (no shortcuts) –Expandable via plug-ins Covers all basic editing and many advanced

Basic Editing Most Important Command: Revert –Under the File Menu –Ctrl-z is undo but only one step. Suggest do “save as” or make copy first so don’t destroy original Resize for web: under Image: Scale or Adjust: Size

Basic Editing Selecting a region Clear Clear outside Cropping Rotating and Flipping Adjusting Brightness and Contrast Thresholding

An Example How symmetrical am I? –The original image

Select the region I used the rectangular region – easier Centered on some feature in middle – find the x value (I used a gap in my teeth)

Crop and Flip CroppedFlipped Horizontally

Cut and Paste Reopen original face Select all of half face Paste into other Adjust location Final Picture

Paste Control Copy Blend

Paste Control Difference Transparent

Converting Images Save as for Image Types – use GIF or JPG –Must add extension, it is not added automatically –Always use save as to save anything other than a TIFF This is a full color uncompressed image

Converting Images Converting Color Depth or to Grayscale image –8-bit, 16-bit, 32-bit are grayscale –8-bit RGB and RGB are color –It is not possible to arbitrarily convert images but ImageJ gives table of possible conversions e.g. can only convert JPG to and 8bit grayscale.

Adding to Images Setting Colors –Edit: Options: Foreground Color –Image: Colors Adding Text –Set font in Edit: Options: Font Draws in selected color

Adding to Images Drawing a basic graphics object –Draw width: Edit: Options: Line Width –Select shape –Put shape on image –Edit: Draw or ctrl-D Filled regions –Same as above, but: line width not important Use Edit: Fill or ctrl-F

Filtering Images Under the Process menu –Sharpen: more edges –Smooth: dull details

Filtering Images Edges: finds them – so type of outline

Filtering Images Gaussian: blurs –Amount of blur depends upon the standard deviation (called radius)

Some Useful Plugins Some have limits but as developments go, you will be able to get new ones without these limits Can build your own –Uses Java –instructions on web page RGB Recolor Inverter File opener: multiple files AVI writer