I am having some problems with the quality of images the JPEG generation
creates. The original image used to create the tiled TIFF is good quality with
a high resolution. I have tried both vips and ImageMagick with the same
result. Basically, if I choose a width that is 1/2, 1/4, 1/8, etc of the
original width, the JPEG looks pretty good, but if I try to size it to a
random number, such as 200, the image does not look as smooth compared to the
original image or using ImageMagick to resize and convert the original TIFF to
JPEG.
I realize there are a lot of variables at play, so I was hoping someone could
help me pinpoint the problem. Is it my initial conversion to a tiled TIFF? I
started by using the conversion parameters provided in the documentation, and
then tweaked and added parameters to see if it did anything. If it has to do
with the width I'm requesting, is it possible to have the server determine the
best width in place of what I requested? I noticed in the forums that this was
the default behavior in past versions (I'm using 0.9.8). Is there a parameter
to go back to this behavior?
Any help would be greatly appreciated! Thanks!
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The multi-resolution TIFF contains resolutions at full resolution, 1/2, 1/4,
1/8 etc. If you ask for a size exactly equal to this, it will simply serve
this resolution as-is, which should be at high quality. For intermediate
sizes, the server does a nearest neighbour interpolation, which is fast, but
not the best quality. But even so, it should be good enough for most purposes.
If you want only the highest quality resizing, you should only ask for the the
1/2, 1/4, 1/8, ... etc sizes. You can easily calculate these sizes from the
original image size.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I am having some problems with the quality of images the JPEG generation
creates. The original image used to create the tiled TIFF is good quality with
a high resolution. I have tried both vips and ImageMagick with the same
result. Basically, if I choose a width that is 1/2, 1/4, 1/8, etc of the
original width, the JPEG looks pretty good, but if I try to size it to a
random number, such as 200, the image does not look as smooth compared to the
original image or using ImageMagick to resize and convert the original TIFF to
JPEG.
I realize there are a lot of variables at play, so I was hoping someone could
help me pinpoint the problem. Is it my initial conversion to a tiled TIFF? I
started by using the conversion parameters provided in the documentation, and
then tweaked and added parameters to see if it did anything. If it has to do
with the width I'm requesting, is it possible to have the server determine the
best width in place of what I requested? I noticed in the forums that this was
the default behavior in past versions (I'm using 0.9.8). Is there a parameter
to go back to this behavior?
Any help would be greatly appreciated! Thanks!
The multi-resolution TIFF contains resolutions at full resolution, 1/2, 1/4,
1/8 etc. If you ask for a size exactly equal to this, it will simply serve
this resolution as-is, which should be at high quality. For intermediate
sizes, the server does a nearest neighbour interpolation, which is fast, but
not the best quality. But even so, it should be good enough for most purposes.
If you want only the highest quality resizing, you should only ask for the the
1/2, 1/4, 1/8, ... etc sizes. You can easily calculate these sizes from the
original image size.