I am reading a large ECW file and clipping out a section then writing it to ECW again. Does anyone know how FME manages ECW compression. The writer by default is set to 75% compression but the ECW file is already compressed. Does the writer honour the original compression settings or is it further compressing a compressed file? Should I set compression to 0%? Also I can't seem to find a concise answer on whether FME now handles ECW v3 images?
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ECW compression from ECW read to ECW write. ECW v3
Best answer by xiaomengatsafe
Hi @garethgis, Thanks for your question.
Regarding ECW v3, we are planning to add this support. The request originated from this idea: https://knowledge.safe.com/idea/60803/support-for-ecw-v3.html. When the new support is added to our beta builds, we will update the idea's status from Suggested to In Beta. It would be awesome if you could add your vote on the idea, and follow updates on it.
In terms of ECW compression, I wonder if this snippet from the Doc http://docs.safe.com/fme/2019.0/html/FME_Desktop_Documentation/FME_ReadersWriters/ecw/ecw.htm is helpful:
"Compression Level: This option sets the desired compression level of the output image. This is expressed as a percentage of the original file size; for example, setting a compression level of 75 means that the output image will be approximately 75% smaller than an uncompressed image (that is, it will be about one-quarter the size of the uncompressed image).
Note: This value only represents the targeted compression level, and this may not actually be achieved. Also note that ECW does not support lossless compression; that is, even if a compression level of 0 is specified, the output ECW file may not be identical to the original image."
This sounds to me means if you'd like to keep the output as close as possible to the original image, we'd recommend setting Compression level of 0, although it may not produce output identical to the original. Does that help you enough on deciding how to set this parameter?
+3- Safer
- Best Answer
Hi @garethgis, Thanks for your question.
Regarding ECW v3, we are planning to add this support. The request originated from this idea: https://knowledge.safe.com/idea/60803/support-for-ecw-v3.html. When the new support is added to our beta builds, we will update the idea's status from Suggested to In Beta. It would be awesome if you could add your vote on the idea, and follow updates on it.
In terms of ECW compression, I wonder if this snippet from the Doc http://docs.safe.com/fme/2019.0/html/FME_Desktop_Documentation/FME_ReadersWriters/ecw/ecw.htm is helpful:
"Compression Level: This option sets the desired compression level of the output image. This is expressed as a percentage of the original file size; for example, setting a compression level of 75 means that the output image will be approximately 75% smaller than an uncompressed image (that is, it will be about one-quarter the size of the uncompressed image).
Note: This value only represents the targeted compression level, and this may not actually be achieved. Also note that ECW does not support lossless compression; that is, even if a compression level of 0 is specified, the output ECW file may not be identical to the original image."
This sounds to me means if you'd like to keep the output as close as possible to the original image, we'd recommend setting Compression level of 0, although it may not produce output identical to the original. Does that help you enough on deciding how to set this parameter?
xiaomengatsafe wrote:
Hi @garethgis, Thanks for your question.
Regarding ECW v3, we are planning to add this support. The request originated from this idea: https://knowledge.safe.com/idea/60803/support-for-ecw-v3.html. When the new support is added to our beta builds, we will update the idea's status from Suggested to In Beta. It would be awesome if you could add your vote on the idea, and follow updates on it.
In terms of ECW compression, I wonder if this snippet from the Doc http://docs.safe.com/fme/2019.0/html/FME_Desktop_Documentation/FME_ReadersWriters/ecw/ecw.htm is helpful:
"Compression Level: This option sets the desired compression level of the output image. This is expressed as a percentage of the original file size; for example, setting a compression level of 75 means that the output image will be approximately 75% smaller than an uncompressed image (that is, it will be about one-quarter the size of the uncompressed image).
Note: This value only represents the targeted compression level, and this may not actually be achieved. Also note that ECW does not support lossless compression; that is, even if a compression level of 0 is specified, the output ECW file may not be identical to the original image."
This sounds to me means if you'd like to keep the output as close as possible to the original image, we'd recommend setting Compression level of 0, although it may not produce output identical to the original. Does that help you enough on deciding how to set this parameter?
Thanks for the answer XiaomengAtSafe. I have added my vote for V3 and the help info is good and answers my question on compression.
+3- Safer
garethgis wrote:
Thanks for the answer XiaomengAtSafe. I have added my vote for V3 and the help info is good and answers my question on compression.
Thanks @garethgis. That's great to hear!
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