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)
-------------
_______________________________________________ Do not post admin
requests to the list. They will be ignored. Quartz-dev mailing
list (em...@hidden) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/quartz-dev/em...@hidden
This email sent to em...@hidden
