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Bringing JPEG 2000 into the GeoWeb
posted by Satri
on Monday November 13, @09:42AM
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from the bringing-the-future-to-the-present dept.
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Geospatial Solutions offers a long and informative article named bringing JPEG 2000 into the GeoWeb. From the article: "JP2 uses wavelet-based algorithms to efficiently store an image at multiple resolutions, removing the need for users to preprocess imagery into “pyramids.” JP2 also uses advanced arithmetic encoding techniques to provide significantly greater image quality than JPEG [...] In addition to high image quality, JP2 supports multiple bands (for multi- or hyperspectral datasets) and signed data and allows for 16 or more bits of precision. These are all features that GIS workflows might require. The JP2 file format also supports storage of more than one image per file, as well as rich colorspace models, user-defined metadata, and more."
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Raster Image Pyramids Tips
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Image Compression: Seeing What's Not There
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st_0x0ef writes "Understanding how an image file can be represented in a small compressed file and how it may be reconstructed it is very helpfull if we want to work efficiently with large dataset. In this article, we will see how a JPEG file represents an image using a fraction of the computer storage that might be expected. We will also look at some of the mathematics behind the newer JPEG 2000 standard.
For those who lack the strong mathematical foundation that is required to understand the stuff from this article, I will try to describe what each format does in more accessible terms. JPEG tries to find blocks with very similar colours and will make one block of this. The compression is obtained because for example instead of having to describe an 8x8 block (which means you have to state 64 times which color the tiny 1x1 block is), you can simply say that the entire block is one colour. JPEG is so successful, because the human eye can only distinguish a limited number of shades of colour, whereas a computer can store quite a lot that we are never able to distinguish." The rest of st_0x0ef's submitted review below, see also the link above for full article with images.
For those who lack the strong mathematical foundation that is required to understand the stuff from this article, I will try to describe what each format does in more accessible terms. JPEG tries to find blocks with very similar colours and will make one block of this. The compression is obtained because for example instead of having to describe an 8x8 block (which means you have to state 64 times which color the tiny 1x1 block is), you can simply say that the entire block is one colour. JPEG is so successful, because the human eye can only distinguish a limited number of shades of colour, whereas a computer can store quite a lot that we are never able to distinguish." The rest of st_0x0ef's submitted review below, see also the link above for full article with images.
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