humm... now i'm getting confused. that method returns an array of
UIColor objects for each pixel in the CGImage. but how am i receiving
the object atX:andY by imputing those values into the method? if i'm
searching for a read-only value to output an NSLog of [UIColor
colorWithRed:green:blue:alpha], where do i get that from? *head is
swimming*
clearly i'm missing something fundamental here.
On Sun, Nov 29, 2009 at 8:26 PM, Waqar Malik <wmal...@gmail.com> wrote:
> Yes, that is then number of pixels, but do you really need that, as the width
> and height would be the same, check those values as well.
>
> --Waqar
> On Nov 29, 2009, at 5:13 PM, Chunk 1978 wrote:
>
>> humm... while i understand most of this method, i don't understand
>> what is passed as "count"? i understand that this will convert a
>> UIImage into a CGImage, and store each pixel of the image into an
>> array, which are indexed by "xx" and "yy" variables. but what is
>> count? is count the total number of pixels of the passed image?
>>
>> ––––––––––
>> + (NSArray*)getRGBAsFromImage:(UIImage*)image atX:(int)xx andY:(int)yy
>> count:(int)count
>> {
>> NSMutableArray *result = [NSMutableArray arrayWithCapacity:count];
>>
>> // First get the image into your data buffer
>> CGImageRef imageRef = [image CGImage];
>> NSUInteger width = CGImageGetWidth(imageRef);
>> NSUInteger height = CGImageGetHeight(imageRef);
>> CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
>> unsigned char *rawData = malloc(height * width * 4);
>> NSUInteger bytesPerPixel = 4;
>> NSUInteger bytesPerRow = bytesPerPixel * width;
>> NSUInteger bitsPerComponent = 8;
>> CGContextRef context = CGBitmapContextCreate(rawData, width, height,
>> bitsPerComponent, bytesPerRow, colorSpace,
>> kCGImageAlphaPremultipliedLast |
>> kCGBitmapByteOrder32Big);
>> CGColorSpaceRelease(colorSpace);
>>
>> CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
>> CGContextRelease(context);
>>
>> // Now your rawData contains the image data in the RGBA8888 pixel format.
>> int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
>> for (int ii = 0 ; ii < count ; ++ii)
>> {
>> CGFloat red = (rawData[byteIndex] * 1.0) / 255.0;
>> CGFloat green = (rawData[byteIndex + 1] * 1.0) / 255.0;
>> CGFloat blue = (rawData[byteIndex + 2] * 1.0) / 255.0;
>> CGFloat alpha = (rawData[byteIndex + 3] * 1.0) / 255.0;
>> byteIndex += 4;
>>
>> UIColor *acolor = [UIColor colorWithRed:red green:green
>> blue:blue alpha:alpha];
>> [result addObject:acolor];
>> }
>>
>> free(rawData);
>>
>> return result;
>> }
>> ––––––––––
>>
>> so could if i had an image of a tree called "tree.png" that's 50
>> pixels in width, and 100 pixels in height, and i want the RGBA color
>> data of the second last pixel of the last row of pixels, would i call
>> it like this:
>>
>> ––––––––––
>> [self getRGBAsFromImage:[UIImage imageNamed:@"tree.png"] atX:49
>> andY:100 count:(50*100)];
>> ––––––––––
>>
>>
>>
>> On Sun, Nov 29, 2009 at 1:28 PM, Chunk 1978 <chunk1...@gmail.com> wrote:
>>>
>>> precisely! thanks for this.
>>>
>>> On Sun, Nov 29, 2009 at 1:24 PM, Waqar Malik <wmal...@gmail.com> wrote:
>>>>
>>>> I think this is what you are looking for.
>>>>
>>>> <http://stackoverflow.com/questions/448125/how-to-get-pixel-data-from-a-uiimage-cocoa-touch-or-cgimage-core-graphics>
>>>>
>>>> On Nov 29, 2009, at 10:17 AM, Chunk 1978 wrote:
>>>>
>>>>> what method, or combination of methods can i use to receive color
>>>>> information of a CGPoint. i can get basic coordinates of a view using
>>>>> UITouch's locationInView method, but i'd like to get an RGBA color
>>>>> information output. what methods or example code from apple should i
>>>>> research?
>>>>>
>
>
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