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POhow can i handling UIImage using a pointer?
 

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  1. POhow can i handling UIImage using a pointer?
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    <p>i'm studying iOS programming.</p> <p>i have to handling an image.</p> <p>i must make an image to BMP file. but iOS doesn't support to make BMP file.</p> <p>so i think that maybe i use a pointer i can make BMP file.</p> <p>i make a header for BMP. and put it in an <code>NSData</code> object.</p> <p>now i left saving image data's to that <code>NSData</code>.(i'll say bmpData)</p> <p>here's start my wondering.</p> <p>i have to have image which size is 128 x 64.</p> <p>i get the <code>UIImage</code> from a context. (i'll say image1)</p> <p>and i make a <code>CGSize</code> which is 128 x 64.</p> <p>i make a context2 using that size, drawing an image1</p> <p>now i get the <code>UIImage</code> from a context2, which size is 128 x 64, resized image1.</p> <p>and i make an <code>UIImageView</code> and use image2, it works fine. good. image2 is made well.</p> <p>so i declared a pointer, which is unsigned char *.</p> <pre><code>unsigned char *bmpDataPointer = (unsigned char *)image2; </code></pre> <p>and i use for loop</p> <pre><code>for(int i = 0; i &lt; 64; ++i) { for(int j = 0 ; j &lt; 128; ++j) { // dataObj and bmpData are different NSData object // dataObj just contain bitmap data to check my pointer works fine or not. [dataObj appendBytes:&amp;(bitmapDataPointer[i*1 + j]) length:sizeof(char)]; } } </code></pre> <p>and i make a <code>UIImage</code> to check that data is valid, it fails.</p> <pre><code>UIImage *createdImageUsedByaPointer = [UIImage imageWithData:dataObj]; if(createdImageUsedByaPointer == nil) { NSLog(@"nil!"); } </code></pre> <p>ok run. then string nil will be presented.</p> <p>why is that? i make context size 128 x 64, so i loop 128 x 64 times.</p> <p>but it works bad.</p> <p>how can i fix that??</p> <p>how can i handling an <code>UIImage</code> to use a pointer??</p> <p>anybody knows about that please help me.</p>
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    1. COWhat is the type of `image2`?
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      1. USAlexander
    2. COimage2 is UIImage
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    3. COYou can't just cast the `UIImage` object to `unsigned char *`. `Because image objects are immutable, they also do not provide direct access to their underlying image data. However, you can get an NSData object containing either a PNG or JPEG representation of the image data using the UIImagePNGRepresentation and UIImageJPEGRepresentation functions.`
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