howto use MagickGetImageHistogram

[ghety]

hi guys
this is my first post

the question: how can i use MagickGetImageHistogram in iPhone SDK (Objective C)?

Simple code

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MagickWandGenesis();
	magick_wand = NewMagickWand();
	NSData * dataObject = UIImagePNGRepresentation([UIImage imageNamed:@"myimage.jpg"]);
	
    MagickBooleanType status;

    status = MagickReadImageBlob(magick_wand, [dataObject bytes], [dataObject length]);
    
	if (status == MagickFalse) {
		ThrowWandException(magick_wand);
	}

PixelWand *p_wand;
    p_wand = NewPixelWand();

I'm interested in the method

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MagickGetImageHistogram(magick_wand, size_t * );

who is "size_t"?

MagickGetImageHistogram is an array or something?

Thanks

[magick]

MagickGetImageHistogram() returns an array of PixelWand's. The second parameter is the number of pixel wands returned in the array:

• pixel_wands = MagickGetImageHistogram( magick_wand, &number_wands);

[ghety]

Thanks magick
but this is my simple code with exit error:

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MagickWandGenesis();
magick_wand = NewMagickWand();
NSData * dataObject = UIImagePNGRepresentation([UIImage imageNamed:@"myimage.jpg"]);
	
MagickBooleanType status;

status = MagickReadImageBlob(magick_wand, [dataObject bytes], [dataObject length]);
    
if (status == MagickFalse) {
	ThrowWandException(magick_wand);
}

PixelWand * p_wand;

p_wand = NewPixelWand();

PixelSetColor(p_wand,"red");

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MagickGetImageHistogram(magick_wand , 1); 

warning: passing argument 2 of 'MagickGetImageHistogram' makes pointer from integer without a cast

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MagickGetImageHistogram(magick_wand , PixelGetColorCount(p_wand)); 

warning: passing argument 2 of 'MagickGetImageHistogram' makes pointer from integer without a cast

I have no idea.

Can you help me to fix the code?

[el_supremo]

Both your examples are wrong. As Magick said, MagickGetImageHistogram returns an array of PixelWands and the second argument is a *pointer* to an integer which *returns* the number of wands (unique colours). You are trying to pass an integer to MagickGetImageHistogram when you should be receiving one from it.
e.g.

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int num_wands;
PixelWand **pw_array;
.
.
.
pw_array = MagickGetImageHistogram(magick_wand , &num_wands);
// Check for valid result
if(!pw_array || !num_wands) {
     // Handle the error - there's no histogram
    .
    .
}
// Now handle the pixel wands returned

Pete