Convert RGB image to 1 channel image (black/white)

Question

How can I convert RGB image to 1 channel image (black/white) using ios5?

Input image is usually a photo of a book page. Goal is to reduce the size of a photocopy by

Answer 1

You can use Core Image to process your image to black & white.

use CIEdgeWork , this will convert your image to black and whie

for more information on Core Image Programming, visit:- https://developer.apple.com/library/ios/#documentation/GraphicsImaging/Conceptual/CoreImaging/ci_tasks/ci_tasks.html#//apple_ref/doc/uid/TP30001185-CH3-TPXREF101

The code you are looking for is probably this:

CIContext *context = [CIContext contextWithOptions:nil]; // 1
CIImage *image = [CIImage imageWithContentsOfURL:myURL]; // 2
CIFilter *filter = [CIFilter filterWithName:@"CIEdgeWork"]; // 3
[filter setValue:image forKey:kCIInputImgeKey];
[filter setValue:[NSNumber numberWithFloat:0.8f] forKey:@"InputIntensity"];
CIImage *result = [filter valueForKey:kCIOutputImageKey]; // 4
CGImageRef cgImage = [context createCGImage:result fromRect:[result extent];