Unit 2 Digital Information. Chapter 1 Study Guide

Transcription

1 Unit 2 Digital Information Chapter 1 Study Guide

2 2.5 Wrap Up Other file formats Other file formats you may have encountered or heard of include:.doc,.docx,.pdf,.mp4,.mov The file extension you often see on a file (ex. CSP.jpg) is really just an indicator to the computer of how the underlying bits are organized, so the computer can interpret them. If you change the name of the file to CSP.gif, that does not magically change the underlying bits; all you ve done is confuse the computer. It won t be able to open the file because it will attempt to interpret the file as a GIF when really the bits are in JPG format.

3 Personal Favicon Walk-Around Open up your Personal Favicon on the Color Pixelation Widget to display Put your Favicon Activity Guide out on your desk opened up to the rubric/questions I will go around and make sure that it is: 16 x 16 size In color An image (not just a pattern) If you printed yours out instead, put the picture out on your desk. You will all go around and see your classmates creative side You will turn in the rubric with questions answered at the end of class

4 Unit 2 Chapter 1 Topics Bytes and File Sizes Text Compression Encoding B&W Images Encoding Color Images Lossy Compression and File Formats

5 2.1 Bytes and File Sizes In this section, we revisited Wordpad to see that each character is stored as 1 byte of data, but the text in Word contains WAY more bytes due to formatting. We then learned about the different prefixes that described the number of bytes. We spent the remainder of the period researching different types of files (text documents, songs, movies, etc.) and their size (i.e. how many bytes they typically take up in storage). Bottom line = files are comprised of a LOT of bytes, which can make file transfer and storage an area of concern Vocab: Bit Byte Kilobyte, Megabyte, Gigabyte, Terabyte

6 2.2 Text Compression In this section, we learned the importance of compression when working with data as a way of increasing efficiency when sending files and as save space in storage of these files. The key is to figure out how to represent the SAME DATA with FEWER BITS. We spent a great deal of time working with the compression widget and looking for patterns (and competing) to make the highest compression percentage Vocab: Compression Lossless vs. Lossy Compression Compression Percentage Algorithm Hueristic

7 2.3 Encoding B&W Images We began this section by creating a protocol for creating a Black and White picture (by hand prior to using a widget), and realized the importance of providing information about the picture (data) prior to the actual creation of the picture (preview of metadata). Then we discovered how to use bits (1 s and 0 s) to create any black and white picture. We ended class by experimenting with different image sizes (in pixels) and the creation of the binary code to make these images. Vocab: Image Pixel Metadata Encoding

8 2.4 Encoding Color Images This lesson revisited hexadecimal as another number system (base 16) and as an easier on the eyes way of representing 4 bits of data. We then spent time converting between decimal, binary, and hexadecimal numbers. The purpose of revisiting hexadecimal was to make the changing of colors in the color pixelation widget easier. This new widget included new metadata the need for bits per pixel (bpp). As the bpp increases, the number of distinct colors also increases. We also watched numerous videos about RBG color schemes and the process of editing picture files. Vocab: Screen resolution Density RGB Colors

9 2.5 Lossy Compression and File Formats We finally saw examples of lossy compression where useless or lessthan-totally-necessary information was thrown out in order to reduce the size of the data. When using the lossy compression app, most of us were still able to decipher the message due to context clues and our ability to piece things together on our own. The majority of this section was spent researching different file formats and the type of compression used (lossless, lossy) if used at all. Vocab: Lossy Compression MP3, JPEG, WAV, GIF, PNG

10 Math Review Solutions # bytes 3000 KB = 3 million bytes 700 MB = 700 million bytes 5 GB = 5 billion bytes

11 Math Review Solutions #2 a. 150 bytes b. 210 seconds = 3.5 minutes * 1 MB/min = 3.5 MB = 3.5 million bytes

12 Math Review Solutions #3 3 GB = 3000 MB / 5 MB = 600 images

13 Math Review Solutions #4 Original Compression = = 41% Original 100

14 Math Review Solutions #5 a. Lossy you are unable to full replicate the original number b. Lossy one of the RGB values is less than 75, therefore would go to O. When trying to reverse the process, that value would become 75 instead of 60. c. Lossless can perfectly recreate the text using the dictionary. d. Lossy JPEG in an example of Lossy compression.

15 Math Review Solutions #6 Adding a single bit will double the number of colors. Ex. 1 bit = 2 colors 2 bits = 4 different colors 3 bits = 8 different colors Ex. Using binary, RGB changed to RRGGBB would multiply the amount of colors by 8.

16 Math Review Solutions #7 Width = 10 (first 8 bits) Height = 3 (next 8 bits) 0= Black 1 = white

17 Math Review Solutions #8 Width = 3 (first 8 bits), Height = 17 (next 8 bits), bpp = 1 (next 8 bits) a. 3 x 17 = 51 pixels b. 1 bpp c. 2 color options (white or black) d. 6 bpp allows 2 bits per RGB, so 4 x 4 x 4 = 64 colors

18 Math Review Solutions #9 Width = 12 (first 8 bits) Height = 6 (next 8 bits) bpp = 12 (next 8 bits) 12 bpp allows 4 bits per RGB and 4 bits = 1 hexadecimal. This would be great to use hexadecimal Decimal: 15, 3, 7 9, 8, 12 6, 7, 6 2, 14, 7 Hex: F37 98C 676 2E7