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.
Images or Graphics on the Screen Pixels: smallest picture element Pixels are not screen dots!!! Several dots (at least three, one of each color) make up each pixel) Bitmat: An array of information that contains the information for the image. It is a 3 dimensional array Width x Height x 24 (8 for each color) So can be huge (.bmp and.tif or.tiff are most common bitmaps)
Graphic and Image Formats Bitmap (bmp, PCT, Tiff) – big, not good for web Graphic Interchange Format (Gif) can animate 8 bits of color – palette or lookup table or LUT – no loss of spatial information Can be some legal issues – make sure the generator legally can generate GIF’s Generally best compression for simple graphics – bad for photos Can generate transparent regions Can Animate
Graphics and Image Formats JPG Generally better for images and photos Spatial not color compression, can distort image spatially and more loss with each save Now can animate as well.
BMP vs JPEG File Sizes Both images are the same relative size..BMP 900kb.JPEG High Quality ~700kb
ImageJ Free at: http://rsb.info.nih.gov/ij/index.html http://rsb.info.nih.gov/ij/index.html Overview Java program Interface a bit awkward because it is free Expandable via plug-ins Covers all basic editing and many advanced - very advanced Scientific quality image editor Used in many technical applications
Basic ImageJ Interface Menus and Tool bars File Open, Save, Save As, Revert Edit Cut, Copy, Paste, Selection, Options Image Basic Image Editing Process More Advanced Image Editing Options Shapes are for selection or drawing. The “A” is for adding text.
Drawing with ImageJ Very simple but easy Access to pixels No anti-aliasing in most drawing modes Downside: jaggies Upside: in complete control of graphics Can store and edit in lots of formats
Aliasing Technical definition: When an image contains frequencies beyond the range of the sampling matrix, the wrap-around and occur as lower frequencies, distorting the image
Aliasing Description of aliasing Generally try to draw and image that has too fine of detail or sharp edges Causes “jaggies” And pixel artifacts That is you can notice the pixels
Effects of Edges Craik-Cornsweet and Minimal Contours Craik-Cornsweet and Minimal Contours Craik-Cornsweet and Minimal Contours
Anti-aliasing Solution to aliasing Bandlimiting or anti-aliasing Essentially blur the edges or image so fine detail is lost In a lot of Software Ideally use a gaussian filter This is the shape of CRT electron beam which is why dots on screen never show up Infante (1985); Silverstein et al. (1990) Many graphics software and even some languages anti-alias (Java2D) but it is not calibrated but good enough with sufficient resolution
Try some When open in ImageJ, all images are bitmaps, but can be edited in different types Basic Graphics Objects Adding Text Saving in Different Format File/Save As
Digital Cameras No loss in Scanning CCD 3.1 Megapixel at least if need photo quality and larger there are 5 megapixel Can use lower image if only need web But do not sacrifice image quality Easy to download Can be 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 White Balance, controls for our color constancy White Balance, controls for our color constancy Effect of the Illuminant Effect of the Illuminant 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 FlashNo Flash Watch for reflections. Can get inexpensive table camera tripods.
Basic Editing in ImageJ Edit a bitmap Most Important Command: Revert Under the File Menu Takes back to last save – careful with saves. 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 Image/Adjust: Size
Basic Editing Often starts with selecting a region Most editing will then occur defined by the selection Edit/Clear Edit/Clear Outside Image/Crop Image/Adjust/Brightness and Contrast
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 Under Image Menu/Type 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)
Plugins These are the heart and sole of ImageJ Some have limits but as developments go on, you will be able to get new ones without these limits How to get: http://rsb.info.nih.gov/ij/plugins/ http://rsb.info.nih.gov/ij/plugins/ Pick desired plug in. Go to ImageJ folder, then to plugins folder I suggest making folders under this to keep organized Restart ImageJ
More on Plugins Can build your own Most built by users Uses Java instructions on web page Some good examples RGB Recolor Inverter File opener: multiple files AVI writer Color Chooser or Color Picker
Creating Shortcuts Under Plugins menu Pick Shortcuts Then Create Shortcut Lists all commands Type letter that will be matched with control button. Under Plugins/Utilities/Shortcuts will show all current shortcuts
Adding Shortcuts Example Pick command JPEG This saves files in a jpeg format A pain to get to usually Use “J” Try ctrl-J
Mail List http://rsb.info.nih.gov/ij/list.html http://rsb.info.nih.gov/ij/list.html Active community of people developing They are very tolerant of idiotic questions. I have personal experience of their tolerance
Assignment Take series of images that you might want shown in sequences as part of a study