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.
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.
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
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 constancy • Effect 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 Flash No Flash
Editing Images with ImageJ • Free at: http://rsb.info.nih.gov/ij/index.html • 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)
Cropped Flipped Horizontally Crop and Flip
Cut and Paste Final Picture • Reopen original face • Select all of half face • Paste into other • Adjust location
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