Playing around with the values I seem to get a spotlight effect by
placing the light position at a y point greater than the height of
the image rect and pointing it at some point in the image. However,
this spotlight seems to be in reverse. While a regular spotlight
would be like having a black stage with a beam of light, lighting a
portion of it, this one is more like a cloud effect. The image is
bathed in white and there is a portion of it visible. Maybe I'm
using the color param incorrectly? But, I'm using white in Quartz
Composer, Core Image Fun House and in my code (1,1,1,1). I've
uploaded a screenshot of the effect as I have it at
http://img519.imageshack.us/my.php?i...icture1na4.png
if you'd like to take a look.
Taking brightness up to 3 gives the following look
http://img205.imageshack.us/my.php?i...icture2nh7.png
This is wierd as the same brightness values in Quartz Composer looks
nothing like this.
Thanks
George
On Jul 11, 2008, at 7:57 PM, Malayil Philip George wrote:
After playing around with the values for a bit and reducing
brightness to 0.3 I kind of get a spotlight effect. But, instead of
a typical spotlight effect where I would have a bright center
surrounded by dark regions, in the displayed effect the
surroundings seems to be covered with white. Not sure why...any
ideas? Thanks
George
On Jul 10, 2008, at 10:42 PM, Malayil Philip George wrote:
Hi,
Does anybody know if there is any sample code to using the
CIFilter CISpotlight. When I use the filter in Quartz Composer, I
get a nice spotlight effect. But, setting the same values in code
results in a totally washed out image with some patches of bright
yellow, blue etc. It's a very strange effect.
[spotlightFilter setDefaults];
CIVector* inputLightPointsAt = [CIVector vectorWithX:200. Y:200.
Z:0.];
NSNumber* inputBrightness = [NSNumber numberWithFloat:1.893];
NSNumber* inputConcentration = [NSNumber numberWithFloat:0.6694];
CIColor* inputColor = [CIColor colorWithRed:1. green:1. blue:1.];
[spotlightFilter setValue: ciImage forKey:@"inputImage"];
[spotlightFilter setValue: lightPosition
forKey:@"inputLightPosition"];
[spotlightFilter setValue: inputLightPointsAt
forKey:@"inputLightPointsAt"];
[spotlightFilter setValue: inputBrightness
forKey:@"inputBrightness"];
[spotlightFilter setValue: inputConcentration
forKey:@"inputConcentration"];
[spotlightFilter setValue: inputColor forKey:@"inputColor"];
CIImage *spotlightOutput = [spotlightFilter
valueForKey:@"outputImage"];
I guess I am not passing the parameters correctly, but, I'm not
sure what's wrong. In CIFilter documentation for CISpotlight I see
inputBrightness
An NSNumber class whose attribute type is CIAttributeTypeDistance
and whose display name is Brightness.
Default value: 3.00 Minimum: 0.00 Maximum: 0.00 Slider minimum:
0.00 Slider maximum: 10.00 Identity: 1.00
Why is minimum and maximum both 0.0? Does slider values refer to
the slider in QuartzComposer? And what does identity mean? Do I
multiply/divide slider value I set in Quartz Composer with the
Identity to arrive at the value I should set in code. It probably
doesn't matter for inputBrightness but inputConcentration has
identity 20 and others null. I have tried various combinations of
number, multiplying and dividing values in QuartzComposer, to no
avail.
I'm a little confused with how to use these params and would
appreciate any help/pointers. Thanks
Regards
George M.P.
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