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Converting RGB to grayscale/intensity

...th 32 bits i.e. 4 bytes per pixel unsigned int fourBytes; unsigned char r,g,b; for (int index=0;index<width*height;index++) { fourBytes=pntrBWImage[index];//caches 4 bytes at a time r=(fourBytes>>16); g=(fourBytes>>8); ...
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How do I escape spaces in path for scp copy in Linux?

..., considering how many spaces it can handle with the same amount of escape characters. Thanks! – Michael Feb 28 '18 at 20:47 add a comment  |  ...
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PHP/MySQL insert row then get 'id'

...); See mysqli_insert_id(). Whatever you do, don't insert and then do a "SELECT MAX(id) FROM mytable". Like you say, it's a race condition and there's no need. mysqli_insert_id() already has this functionality. share ...
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How to update a menu item shown in the ActionBar?

... set a condition in oncreateOptionMenu(). For example: Boolean mISQuizItemSelected = false; /** * Called to inflate the action bar menus * * @param menu * the menu * * @return true, if successful */ @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu ite...
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What is a “callback” in C and how are they implemented?

...ude <string.h> typedef struct { int iValue; int kValue; char label[6]; } MyData; int cmpMyData_iValue (MyData *item1, MyData *item2) { if (item1->iValue < item2->iValue) return -1; if (item1->iValue > item2->iValue) return 1; return 0; } int cmpMyDa...
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Can hash tables really be O(1)?

...TW - concrete example - Visual C++'s std::hash of textual keys combines 10 characters evenly spaced along the text into the hash value, so it's O(1) regardless of text length (but massively more collision prone than GCC!). Separately, claims of O(1) have another assumption (normally correctly) that...
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android get real path by Uri.getPath()

... This is what I do: Uri selectedImageURI = data.getData(); imageFile = new File(getRealPathFromURI(selectedImageURI)); and: private String getRealPathFromURI(Uri contentURI) { String result; Cursor cursor = getContentResolver().query(cont...
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How to automatically generate N “distinct” colors?

I wrote the two methods below to automatically select N distinct colors. It works by defining a piecewise linear function on the RGB cube. The benefit of this is you can also get a progressive scale if that's what you want, but when N gets large the colors can start to look similar. I can also imagi...
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Django ManyToMany filter()

...d it. the above code will end up generating SQL that looks something like: SELECT * FROM users WHERE id IN (SELECT user_id FROM userzones WHERE zone_id IN (1,2,3)) which is nice because it doesn't have any intermediate joins that could cause duplicate users to be returned ...
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@synthesize vs @dynamic, what are the differences?

... [invocation setReturnValue:&obj]; } } @end int main(int argc, char **argv) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; Book *book = [[Book alloc] init]; printf("%s is written by %s\n", [book.title UTF8String], [book.author UTF8String]); book.title = @"...