image manipulation using slider in iphone

Question

Is there a way to apply brightness to uiimages. For example I have a UIImageview and inside that i have a uiimage. I want to manipulate its brightness with a help of UISlider wi

Answer 1

Have a look at Apple's demo app GLImageProcessing , it's really fast:

Answer 2

here is the code:-

        CGImageRef inImage = currentImage.CGImage;
        CFDataRef ref = CGDataProviderCopyData(CGImageGetDataProvider(inImage)); 
        UInt8 * buf = (UInt8 *) CFDataGetBytePtr(ref); 
        int length = CFDataGetLength(ref);
        float value2 =  (1+slider.value-0.5);
        NSLog(@"%i",value);
        for(int i=0; i<length; i+=4)
        {


            int r = i;
            int g = i+1;
            int b = i+2;

            int red = buf[r];
            int green = buf[g];
            int blue = buf[b];


            buf[r] = SAFECOLOR(red*value2);
            buf[g] = SAFECOLOR(green*value2);
            buf[b] = SAFECOLOR(blue*value2);
        }

        CGContextRef ctx = CGBitmapContextCreate(buf,
                                                 CGImageGetWidth(inImage), 
                                                 CGImageGetHeight(inImage), 
                                                 CGImageGetBitsPerComponent(inImage),
                                                 CGImageGetBytesPerRow(inImage), 
                                                 CGImageGetColorSpace(inImage),
                                                 CGImageGetAlphaInfo(inImage));

        CGImageRef img = CGBitmapContextCreateImage(ctx);

        [photoEditView setImage:[UIImage imageWithCGImage:img]];
        CFRelease(ref);
        CGContextRelease(ctx);
        CGImageRelease(img);

define this at the top:-

      #define SAFECOLOR(color) MIN(255,MAX(0,color))

Answer 3

Open Gl to UIImage Create

-(UIImage *) glToUIImage {

NSInteger myDataLength = 320 * 480 * 4;
 // allocate array and read pixels into it.
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, 320, 480, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

// gl renders "upside down" so swap top to bottom into new array.
// there's gotta be a better way, but this works.
GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
for(int y = 0; y <480; y++)
{
    for(int x = 0; x <320 * 4; x++)
    {
        buffer2[(479 - y) * 320 * 4 + x] = buffer[y * 4 * 320 + x];
    }
}
// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(
                                                          NULL, buffer2, myDataLength, NULL);

// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * 320;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();

CGBitmapInfo bitmapInfo = kCGImageAlphaNone;

CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

// make the cgimage
CGImageRef imageRef = CGImageCreate(320, 480, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

// then make the uiimage from that


UIImage *myImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

//UIImageWriteToSavedPhotosAlbum(myImage,nil,nil,nil);

[[NSUserDefaults standardUserDefaults] setObject:UIImageJPEGRepresentation(myImage,1) forKey:@"image"];    

return myImage;

}