Hi all
I have a django asset management tool that uses the exiftool command
line to extract metadata which does get the title, and a host of other
tags. Exiftool is great because it's complete and really well
maintained. The downside is of course that it's perl. I use the
command line interface through subprocess, works really well.
Geert
On Jun 3, 2009, at 12:35 AM, [email protected] wrote:
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Today's Topics:
1. Re: Lanczos interpolation (Franz Buchinger)
2. Re: Reading title EXIF data (Franz Buchinger)
3. Python Core Graphics Question (resent) (Geert Dekkers)
From: Franz Buchinger <[email protected]>
Date: June 2, 2009 1:58:38 PM GMT+02:00
To: [email protected]
Subject: Re: [Image-SIG] Lanczos interpolation
A good old trick is to work with intermediate images: resize the
image using the Bilinear method and produce an intermediate image
that is about 25% larger than the final image.
Then you can downscale the intermediate image using Lanczos.
This should give a much better performance than working just with
Lanczos, especially for large downscaling ratios (e.g. 10 Megapixel
JPEG -> 1024x768) .
Image quality shouldn't be affected too much by this method.
Franz
2009/5/12 Fredrik Lundh <[email protected]>
On Sun, May 10, 2009 at 12:45 PM, David Yan <[email protected]>
wrote:
> I want to resize an image Lanczos interpolation but I haven't
found any
> python module that can do so. Also, I'm not knowledgeable enough
to write
> one myself. What's the best way I can do this? I use PIL
currently but the
> resampling filters don't suit my needs (antialias is too slow,
bilinear and
> bicubic produce aliasing when downsampling).
ANTIALIAS is a Lanczos interpolation written in C, so it's not
entirely obvious to me how you expect a Python version to be faster...
</F>
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From: Franz Buchinger <[email protected]>
Date: June 2, 2009 2:12:34 PM GMT+02:00
To: [email protected]
Subject: Re: [Image-SIG] Reading title EXIF data
PIL is an excellent image processing library, but unfortunatly not a
tool of choice when you want to deal with EXIF data seriously.
It only extracts a subset of the EXIF-Data contained in an image,
for a more complete library you may want to check pyexiv2 (python
wrapper for exiv2).
And beware, EXIF (as well as other metadata standards like IPTC) is
full of "dead tags" that are only written by some exotic image
processing applications or camera models.
In your special case ("finding a title for a photo"), I'd resort to
IPTC:Caption - this is where Photoshop/Lightroom/Google Picasa and
many other image processing apps store "title" information.
Franz
2009/5/22 Luke Hutscal <[email protected]>
Hello, all.
I am currently working on a Django application that stores photos as
users upload them.
One of the cooler features that we'd like to add is automatic EXIF
reading - so instead of users having to go through and update their
photo's information again after uploading them, the EXIF data on the
uploaded photos can get automatically read into certain fields -
title, caption, and so on.
I have been using the Image._getexif() method to retrieve the EXIF
data for the photos that are being uploaded - but it seems that the
"title" attribute is missing. Here's an example of what _getexif()
returns:
http://liftslice3.com/getexif.txt
However, when I run ExifTool(http://www.sno.phy.queensu.ca/~phil/exiftool/
) on the image with the -d flag, this is what is output:
http://liftslice3.com/exiftool.txt
As you can see, there's definitely a title attribute present on the
image in question. I took a look at the EXIF tags list at http://www.element-it.com/StandardImageTags.ASPX
, and noticed that the ImageTitle EXIF tag isn't present in PIL's
ExifTags.py - is there a reason for this? I tried adding a key for
0x0320 with the value "ImageTitle" to the TAGS dict, but PIL still
doesn't seem to be reading the ImageTitle attribute out of my images.
Is there something I've missed that is keeping PIL from reading the
title attribute?
Thanks,
Luke
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From: Geert Dekkers <[email protected]>
Date: June 2, 2009 9:13:50 PM GMT+02:00
To: [email protected]
Cc: [email protected]
Subject: [Image-SIG] Python Core Graphics Question (resent)
Hi all
(I just resent this message as I couldn't it find it on the digest
even after days - again, I apologise for any cross-posting)
Below is a piece of code that I found over in the quartz-dev list.
I've been using this function unchanged in a batch processor, and it
appears to leak memory quite substantially. So much so that my test
machine (1Gb memory) , a mac mini, and my production xserve (2 Gb
memory) both crashed using it. My dev machine, an imac (4Gb memory)
slowed, but stayed up.
I think I have the problem down to "croppedimg =
srcimg.createWithImageInRect(cliprect)". If used with an image of
suffient size, it quickly sucks up all available memory.
Has anyone experienced similar problems using this method? Its Obj-C
name is "CGContextCreateWithImageInRect". And I should think that
one would only see something bad happening in some sort of batch
processing.
Incidentally, my workaround was to lower the size of the source
image. But the process is still quite unstable. It brought down my
xserve after processing 7000 of the 7600 odd items.
I've pasted the original post below. And sorry for any cross -
posting.
Cheers, Geert
----------------------------------------------------------------------------------------------
Geert Dekkers Web Studio | 2e Keucheniusstraat 8HS 1051VR Amsterdam
| +31(0)627224301 | http://nznl.net
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Thanks for you detailed reply Glen - much appreciated.
You helped me to solve what i was trying to do by using
CGImageCreateWithImageinRect as suggested.
For anyone else interested here is some simple python code for
making cropped thumbnails of any proportion and not loosing the
aspect ratio of the original image.
...and its damn fast!
----------- #!/usr/bin/python
from __future__ import division import CoreGraphics
def resizeimage(srcimage,targetimage, tw, th):
srcimg =
CoreGraphics
.CGImageImport
(CoreGraphics.CGDataProviderCreateWithFilename(srcimage))
sw = srcimg.getWidth()
sh = srcimg.getHeight()
aspect = tw/th
widthfactor = tw/sw
heightfactor = th/sh
if widthfactor < heightfactor:
#src height stays the same
#src width gets cropped
cropwidth = sh * aspect
x1 = ((sw-cropwidth)/2)
y1 = 0
x2 = sw-((sw-cropwidth))
y2 = sh
else:
#src height gets cropped
#src width stays the same
cropheight = sw / aspect
x1 = 0
y1 = ((sh-cropheight)/2)
x2 = sw
y2 = sh-((sh-cropheight))
cliprect = CoreGraphics.CGRectMake(x1, y1, x2, y2)
croppedimg = srcimg.createWithImageInRect(cliprect)
cs = CoreGraphics.CGColorSpaceCreateDeviceRGB()
c = CoreGraphics.CGBitmapContextCreateWithColor(tw, th, cs,
(0,0,0,0))
c.setInterpolationQuality(CoreGraphics.kCGInterpolationLow)
newRect = CoreGraphics.CGRectMake(0, 0, tw, th)
c.drawImage(newRect, croppedimg)
c.writeToFile(targetimage, CoreGraphics.kCGImageFormatJPEG)
resizeimage("/users/adam/Desktop/bootlogo4pa8.jpg", "/users/adam/
Desktop/aaaaa.jpg" , 80,80)
On Aug 12, 2008, at 3:41 AM, Glenn Cole wrote:
Hi, Adam --
I'm no expert, but until others more knowledgeable respond,
here's my understanding.
First, I suspect the fact that you're using Python won't matter
at all here. (It does in other circumstances, but I don't think
so here.)
It sounds like you're looking for more support from Quartz for
your task than what's really there. In the end, I think it's
going to be more a choice of algorithm on your part.
For example, given different aspect ratios, the new image could
either:
1. ignore the difference (i.e., the current behaviour)
2. show the entire original image within the new target,
respecting the aspect ratio
3. clip the original image to match the new aspect ratio
For #2, you could shrink the target rect to match the aspect
ratio of the original image.
For #3 (your goal), you could clip the original image to match
the target aspect ratio. However, page 250 of the outstanding
Programming With Quartz notes a few downsides to this, and
suggests using CGImageCreateWithImageInRect instead (first
available in Tiger) to define a "subimage" of the original image.
Again, though, you would need to determine yourself that the
subimage should ignore 100 pixels from the left and right sides
of the original image.
At least, that's my take on things. We'll see what others say
(though they've tended to ignore Python questions in the past).
Incidentally, the subject line says "Core Image resize question."
The code below has no reference to Core Image, and I'm pretty
sure that Core Image need not be involved in this task at all.
(Perhaps you mentioned Core Image because of the existence of its
CICrop filter, but I think that's not the best direction for the
task at hand.)
--Glenn
On Aug 11, 2008, at 5:33 AM, Adam Jones wrote:
Hi there i am wondering if someone can help me with this. Below
is the code i am using to resize and save a jpeg image.
It works mint as but it obviously scales the image with no
respect for the aspect ratio.
i want to be able to take an image and scale it proportionaly to
a square thumbnail. so for example a 800x600 image scaled to
80x80 would need to loose 100pixels off the left and 100 pixels
on the right before scaling.
Does any one know how to crop using python quartz or can i draw
the rec with the image off the canvas to achieve the same?
Thanks Adam
----------- #!/usr/bin/python
import CoreGraphics
def resizeimage(srcimage,targetimage, w, h):
origImage = CoreGraphics .CGImageImport
(CoreGraphics.CGDataProviderCreateWithFilename(srcimage))
origwidth = origImage.getWidth() # not used yet but will be once
i work out how to crop
origheight = origImage.getHeight() # not used yet but will be
once i work out how to crop
cs = CoreGraphics.CGColorSpaceCreateDeviceRGB()
c = CoreGraphics.CGBitmapContextCreateWithColor(w, h, cs,
(0,0,0,0))
c.setInterpolationQuality(CoreGraphics.kCGInterpolationLow)
newRect = CoreGraphics.CGRectMake(0, 0, w, h)
c.drawImage(newRect, origImage)
c.writeToFile(targetimage, CoreGraphics.kCGImageFormatJPEG)
resizeimage(uploadedfile, "/svr/data/images/listings/%s/
%s_160x90.jpg" % (str(listing_id), newimagename), 160,90)
-------------
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