Byte Array to UIImage Objective-C

Question

I have a Bytearray

unsigned char *outputData = (unsigned char *)malloc(sizeof(unsigned char) * w * h * 4);

    outputData[y * h * 4 + x * 4 + 0] = all; //alpha value
    outputData[y * h * 4 + x * 4 + 1] = red; //red value
    outputData[y * h * 4 + x * 4 + 2] = gre; //green value
    outputData[y * h * 4 + x * 4 + 3] = blu; //blue value

            //h... total image height
            //y,x ... current y and x value from the matrix

Now I want to convert this Data to an UIImage. How does that work? I've tried:

NSData *outdata = [NSData dataWithBytes:outputData length:sizeof(unsigned char) * w * h * 4];
UIImage *newimage = [UIImage imageWithData:outdata];

But this doesn't seem to be the right solution. Please help.

OK I think I solved it.. I found out that imageWithData is just creating images which have a format (png, jpeg) .. so I need to create a context first right? — Marco
– Marco, Commented Jul 12, 2011 at 6:55

Jhaliya - Praveen Sharma · Accepted Answer · 2011-07-12 07:01:34Z

11

    CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB();
    CGContextRef bitmapContext=CGBitmapContextCreate(outputData, w, h, 8, 4*w, colorSpace,  kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault);
    CFRelease(colorSpace);
    free(outputData);
    CGImageRef cgImage=CGBitmapContextCreateImage(bitmapContext);
    CGContextRelease(bitmapContext);

    UIImage * newimage = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);

edited Jul 12, 2011 at 7:01

Jhaliya - Praveen Sharma

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answered Jul 12, 2011 at 6:59

Ilanchezhian

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3 Comments

Marco Over a year ago

Thank you very much. Worked perfect. (Just had to change kCGImageAlphaPremultipliedLast to kCGImageAlphaPremultipliedFirst)

SoManyGoblins Over a year ago

Please mark this answer as the correct one, since it worked ;)

emrahgunduz Over a year ago

If you need BGRA convertion, use kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Little instead for bitmap info.

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