.TIF vs .ECW Raster

[ziya...@gmail.com]

Hi,

 

I have found MapInfo struggles to run .TIF based raster files. The system runs very slowly where as an .ECW of comparative file size (or even larger) will run perfectly fine.

 

Does anyone know the reasoning for this?

 

Cheers

 

Ziyaad

[Mats Elfström]

Hi Ziiyad!

ECW is a much more efficient compression scheme, especially for GIS purposes. Among other things, ecw can carry its georeference within the file, and not rely on the limited world file setup.

If you compare tif and ecw in other systems, you probably will notice the same difference in performance.

However, different GIS may use different libraries for reading tifs and ecws, which also can affect performance.

Regards, Mats.E

2013/7/4 <ziya...@gmail.com>

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[ktgcad]

I think i encountered same problem using tif and tfw files in MI..The problem exist in tfw..open tfw file using notepad, you will find unwanted 0000 in it...erase it,,you might have no issues..

Kalai Selvan.K

KTG Infotech

GIS (Mineral Exploration)
Data Integration, Analysis, Capturing and Data Conversion
for Geochemistry,IP and Drill logs
Skypes-ktgcad

[Richard Greenwood]

ECW files use a wavelete compression (https://en.wikipedia.org/wiki/Wavelet_transform)that creates image files that are in the order of 1/10th to 1/20th the size of uncompressed files. So MapInfo needs to read less data from the disk. But the real performance improvement comes from the formats ability to generate virtual pyramids. When you display a 1000x1000 pixel image on a computer monitor that is based on a 10,000x10,000 pixel image then the image must be downsamplesd and 100x as many pixels must read read from the disk than are actually required. A traditional approach to this is to create "pyramids" which are preprocessed for certain zoom levels and only read the

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[Richard Greenwood]

ECW files use a wavelete compression (https://en.wikipedia.org/wiki/Wavelet_transform) that creates image files that are usually 1/10th to 1/20th the size of uncompressed files. So MapInfo needs to read less data from the disk.

But the real performance improvement comes from the ECW format's ability to generate virtual pyramids. When you display a 1000x1000 pixel image on a computer monitor that is based on a 10,000x10,000 pixel image then the image must be down samplesd and 100x as many pixels must read read from the disk than are actually required. A traditional approach to this is to create "pyramids" which are several files that have been down sampled for certain zoom levels and only read the one that is the appropriate resolution for a given display scale. ECW and SID formats have this ability "built-in". There are also certain TIFF formats that can do this but MapInfo's support of the various TIFF format options is very limited and I don't believe it supports and of these.

ECW and SID are proprietary formats that require licenses to read and write. TIFF and JPEG are open formats.

Rich

On Thu, Jul 4, 2013 at 12:09 AM, <ziya...@gmail.com> wrote:

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