Image Objects 1

[jawalsh]

After reading and watching this week's materials, address the following prompts:

• Explain the difference between lossless and lossy compression. Provide an example of each.
• Explain the difference between raster graphic (bitmap image) formats and vector graphic formats. Which format (raster or vector) is produced by an image scanner or digital camera?
• What is an appropriate archival file format for a collection of digitized photographs?
• List any questions or comments about this week’s material.

You are encouraged to read and respond to other discussion posts. Engaging with other students in our online discussions will contribute to your participation grade.

[KatMEdom]

1. Lossless compression compresses the file while retaining all of its data in its original form so that once it is uncompressed all of the information is restored. Lossy compression is the opposite in that when the file is compressed, data considered unimportant will be discarded--often permanently--to further reduce the file size.
2. Raster graphics are made up of pixels. The higher the number of pixels, the better the image quality, and the bigger the file size. Vector graphics are usually made up of geometric shapes, which makes them more scalable than raster graphics. Raster graphics are generally more common and are usually used for images created by a scanner or digital camera.
3. The Library of Congress lists TIFF, JPEG2000, PNG, and JPEG/JFIF as the preferred file formats for digital photographs.

[alamorri]

Good point about how the number of pixels relates to image quality.

[rachknig]

• Lossless compression shrinks the size of the file without losing any data, and the file can be uncompressed with everything intact. An example of lossless compression is the PNG image format. Lossy compression removes some data when compressing, with portions that are considered unimportant discarded to reduce file size. An example of lossy compression is the JPEG image format.
• Raster graphics are two-dimensional images composed of square pixels, while vector graphics are images created by geometric shapes - vectors can even include curves. Most image formats, including those used by scanners and cameras, use raster graphics.
• An appropriate archival file format for digitized photographs is TIFF.
• Are all the file formats mentioned in the textbook still used?

[alamorri]

I didn't think of the example being in regards to file format instead of how files are compressed and decompressed.

[mvladoiu]

Explain the difference between lossless and lossy compression. Provide an example of each.
Lossless compression means the decompressed result is EXACTLY the same file as the original, while lossy decompression means the decompressed result may have minor distortions. Lossless compression is used for text representation, while lossy compression can be used for digitized images and audio. An example of lossless compression is Huffman coding, while an example of lossy compression is quanitzation.

Explain the difference between raster graphic (bitmap image) formats and vector graphic formats. Which format (raster or vector) is produced by an image scanner or digital camera?
Raster graphic refers to pictures that are represented as a rectangular grid of pixels, and is characterized by the width and height of the image in pixels as well as the number of bits per pixel. Vector graphic refers to images that are created from geometric shapes on a Cartesian plane. Raster graphics are used more commonly, and are more appropriate for photography and remote sensing, whereas vector graphics are used for engineering, architecture, surveying, 3D rendering, and typography. Image scanners and digital cameras are raster formats.

What is an appropriate archival file format for a collection of digitized photographs?
TIFF or JPEG2000 would be most appropriate archival file formats for a collection of digitized images.

List any questions or comments about this week’s material.
I didn't realize you could have a non-animated gif! I thought it was inherent to the format that they were animated.

[WayneHastings]

Good point about the non-animated gif! Was also curious about this!

[JohaknigIU]

Explain the difference between lossless and lossy compression. Provide an example of each.
Lossless compression is a higher quality form of compression that allows for images to be converted back to it’s base format and keeps all attached metadata. An example would be PNG files. Lossy compression is a lower quality but lower size compression that is irreversible and deletes some metadata from the image. An example would be JPEG files. This is why PNGs are often higher quality and larger files than JPEGs.
Explain the difference between raster graphic (bitmap image) formats and vector graphic formats. Which format (raster or vector) is produced by an image scanner or digital camera?
Raster graphics are 2D images drawn from individuals pixels, while vector graphics are drawn from geometric shapes. Raster graphics must draw greater pixels horizontally and vertically to scale images, while vector graphics are easily scalable. Most computers, phones, and digital screens today use raster graphics, including images produced from digital cameras and image scanners.
What is an appropriate archival file format for a collection of digitized photographs?
An appropriate archival file format for a collection of digitized photographs would be TIFF files.
List any questions or comments about this week’s material.
While most computers and digital media use raster graphics today, in the 1980’s there was a video game system called the Vectrex that used vector graphics. Because of this the system came with its own built-in screen to render properly, albeit exclusively in black and white. See it in action here!

[heidi-y]

Thanks for that Vectrex example! That was fun to check out.

[heidi-y]

Question 1
Compression can be lossless, meaning that the decompressed file is the exact same file as the original. Lossy on the other hand, means that the decompressed file is not guaranteed to be the same as the original and includes small distortions. Lossy compressions can be a good choice when you need to compress large quantities or when small distortions won't have a big impact on the file. Lossy compression is often used with audio files where small distortions in the audio file are not usually perceptible. However, lossless compression is the only sensible option for text image representation, like a scan of a newspaper article that is being preserved in an archive. (Whitten et al. pg. 216-217).

Question 2
Raster graphics (bitmap graphics) are "a rectangular matrix or grid of square pixels," (Wikipedia.org) and are stored in image files (GIF, JPEG, PNG). Vector graphics are a type of computer graphic in which visual images are created from geometric shapes defined on a Cartesian plane (Wikipedia.org). Vector graphics may include hardware for display and printing, Vector data models and file formats, and software based on said data models. Vector graphics are found in SVG, WMF, EPS, PDF, CDR, or AI formats. As you may be able to tell from that list, images produced by an image scanner or digital camera are produced in Raster graphic formats.

Question 3
According to the LOC's list of appropriate format for digital images, TIFF, JPEG2000, and PNG are all acceptable. However, for archival images, Witten et al suggest TIFF and JPEG2000.

Question 4
When I read the term "lossy compression" I immediately thought it would be a bad thing and something to avoid. I never would have guessed that it's actually something you might choose when compressing your files, or even that it could actually improve multimedia files in certain cases.

[Kschu97]

Great point regarding lossy compression. I initially thought lossy was a bad thing as well.

[SethCope96]

1. Lossless compression preserves the integrity and quality of images, leaving the image itself unchanged. Lossy compression minimizes both size of the file and quality of the file, and the loss in quality might be noticeable when decompressing the file. Lossless compression is helpful when working with PDFs or other images of text, while lossy is the preferred method for many audio and image files due to space constraints.
2. Raster graphics are images that have been represented through the coloration of a rectangular matrix of square pixels, and are 2 dimensional in shape and scope. Vector graphics represent images through the manipulation of shapes and mathematical formulas on a grid. Scanners and digital cameras preserve images in raster formats.
3. You should use JPEG2000 or TIFF format for archival images, or you could also utilize PNG format if you are following the Library of Congress instructions.

[Kschu97]

Explain the difference between lossless and lossy compression. Provide an example of each.
With lossy compression, some of the information is permanently lost such as some pixels upon compression in a JPEG file whereas in lossless compression the file can be compressed without loss of information and later returned to its original size at a later date such as in a PNG file.
Explain the difference between raster graphic (bitmap image) formats and vector graphic formats. Which format (raster or vector) is produced by an image scanner or digital camera?
Raster graphic formats portray images utilizing pixels and tend not to scale well while vector graphic formats utilize lines and curves to portray images and scale well. Raster graphic are what are usually used by an image scanner or digital camera.
What is an appropriate archival file format for a collection of digitized photographs?
An appropriate archival file format for a collection of digitized photographs is JPEG/JIFF if one follows Library of Congress recommendations. A file recommended by Witten et al is the TIFF format.
List any questions or comments about this week’s material.
Is the Digital Information course just for our information? If not, how are we applying the information it covers, specifically the early parts of it?

[absuddar]

1. Lossless compression results in a compressed file that that exactly the same as the original file. Lossy compression results in a compressed file that can include, often unnoticeable, distortions. Lossy compression allows for more compression than lossless. Lossless compression is the only type of compression used for text files (such as PDF’s) and lossy compression is often used for audio files.
2. Raster graphics use a grid of pixels to display a two-dimensional picture on a screen. Vector graphics are created from geometric shapes and are more appropriate for engineering and architecture. Raster graphics are used by image scanners and digital cameras.
3. TIFF files are appropriate for a collection of digitized photographs.

[WayneHastings]

1. Lossless refers to when “the original pixel values can be perfectly regenerated from the compressed data” (Wikipedia), while lossy compression does not have this ability it is only an estimate of the original pixel values. Common examples for lossless include LZW or RLE, while the most common example for lossy is JPEG.
2. Raster graphics are the formats produced by a digital camera. The raster format produces a 2D image that is made up of pixels, while the vector format produces images using lines and curves. It is a direct substitute for raster and also can produce 3D images, rather than just 2D images.
3. According to the Library of Congress, TIFF, JPEG2000, PNG, and JPEG/JFIF are all appropriate file formats for a digital collection of photographs.
4. Is there a preference for either raster or vector if you are printing certain colors?

[casemach]

1. Lossless compression is when the result of a decompressed file is the same as the original file. Lossy compression is when the decompressed file is not the same as the original file since it often contains minor distortions that are not noticeable. Text representation typically uses lossless compression, such as PostScript, PDF, and Open Document formats. Digitized images and audio typically use lossy compression.
2. Raster graphics are two-dimensional images made up of pixels, and are displayed via computer display, paper, or other display medium. Vector graphics are images made up of geometric shapes such as such as points, lines, Curves and polygons. Raster graphics are produced by an image scanner or digital camera.
3. TIFF is an appropriate archival file format for a collection of digitized photographs.
4. Last year I took Digital Curation with Dr. Donaldson, and we did some listening comparisons to audio files that underwent lossless and lossy compression. Unless you really know what to look or listen for, the minor distortions really are unnoticeable!

[layilin]

Lossy compression (e.g. JPEG format) "[eliminates] the noise [and] achieves economy while simultaneously increasing image quality" (Witten et al. 235), whereas lossless compression (e.g. GIF and PNG formats, the former supporting animated images) allows exact reconstruction of the original (in Winnie's words, reducing the size without degrading the visual quality).

Raster graphic formats (JPEG, GIF, PNG, etc.) are effective and efficient for two-dimensional representation and vector graphic formats (SVG) are preferred for engineering, architecture, surveying, 3D rendering, and typography. An image scanner or digital camera produces raster graphic formats.

What is an appropriate archival file format for a collection of digitized photographs?
The digital library of photographs in Witten et al. used JPEG. I think the appropriate archival format depends on how much detail the collection attempts to represent. I would expect a collection on photography to display images of lossless compression but offer RAW format file downloads, if available.

[rthedrick91]

Explain the difference between lossless and lossy compression. Provide an example of each.
Lossless data compression is a type of compression that allows data that has been compressed to be completely restored to its original form. Lossy data compression is the opposite of lossless in that it is a style of compression that permanently cuts out parts of data for the sake of compression.

Explain the difference between raster graphic (bitmap image) formats and vector graphic formats. Which format (raster or vector) is produced by an image scanner or digital camera?
A raster graphic is a format that is a two-dimensional picture that is represented through the arrangement of pixels in a grid. A vector graphic is a type of computer graphic represent through the use of geometric shapes such as polygons. Raster graphics are the more effective format for producing images from a scanner or through digital photos.

What is an appropriate archival file format for a collection of digitized photographs?
According to the LOC's statement on recommended formats for digital photography, the preferred formats for a collection of digitized photos are TIFF, JPEG2000, PNG,JPEG/JFIF, and BMP.

[alamorri]

• Lossless compression is the compression of a larger file without losing any of the data within it. An example would be a picture which is compressed but still retains its original definition (i.e. number of pixels). On the other hand, lossy compression happens when some data of a file is lost when it is compressed, like if the aforementioned picture was compressed and lost some of its pixels.

• Raster graphics are made up of square pixels which are arranged in a rectangular grid, whereas vector graphics are created using geometric shapes. Raster graphics are produced by an image scanner or digital camera.

• GIF would be an appropriate file type for a collection of digitized photographs.

[jawalsh]

While GIF uses lossless compression, the format is limited to 256 colors, so it would not be appropriate for a collection of high-quality digitized photographs. 256 colors is not enough to capture the nuances in color of a photograph.

[ElioSilva]

1. Lossless compression, also known as reversible compression, restores and rebuilds file data in its original form after the file is decompressed. For example, when a picture's file size is compressed, its quality remains the same. That is, the file can be decompressed to its original quality without any loss of data. On the other side, lossy compression is about the data in a file which is removed and not restored to its original form after decompression. Specifically, data is permanently removed, which is why this method is also known as irreversible compression.
2. A raster graphic represents a two-dimensional picture as a rectangular matrix or grid of square pixels, viewable via a computer display or other display medium. Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, Curves and polygons. Most image formats, including those used by scanners and cameras, use raster graphics.
3. According to Witten et al, is recomendable TIFF, which stands for Tag Image File Format, and JPEG2000(JP2), which is an image compression.
4. Is there an external way or a program that helps to revert the original state of an image or files that have been irreversibly compromised (Lossy compression)?

[rachknig]

I believe that you can attempt to restore files which have undergone lossy compression, but it's impossible to perfectly return them to their original state - that's why lossless compression is important when the original state of a file matters, and why archives tend to maintain higher quality versions of digital objects as backups.

[ElioSilva]

Thank you!, I'll keep it in mind.

[cschev]

1. Lossless compression results in no loss of information, as the decompressed result is the same file as the original. An example of lossless compression is the PNG format. Lossy compression cannot guarantee that the decompressed file is the same as the original, as it includes minor distortions. An example of lossy compression is the JPEG format.

2. Raster graphics, which are produced by image scanners and digital cameras, are two-dimensional images made up of pixels that can be displayed on a computer monitor, paper, or other medium. Vector graphics are images made up of geometric shapes such as such as points, lines, curves and polygons

3. The Tiff file format would be appropriate for digitized photographs.