Re: NSBitmapImageRep - draws in 32bit, but not in 16bit depth [SOLVED]

FROM : Jens Bauer
DATE : Sat Nov 02 20:44:29 2002

Hi all,

Solved this problem.

I did 2 things wrong.

1: The alpha channel...
   [offscreen orPlotX:x y:y with:0x00400000];
...should be...
   [offscreen orPlotX:x y:y with:0x004000ff];

2: in the init method, I added...
       [self setCacheMode:NSImageCacheNever];
...so now it looks something like this:
       [self addRepresentation:bitmapImageRep];
       [self setSize:imageSize];
       [self setFlipped:YES];
       [self setCacheMode:NSImageCacheNever];
   }

I hope this will help someone else. =)

Friday 1. Nov 2002 kl. 22:00 skrev Jens Bauer:

> Hi all,
>
> Got some code, which allocates a NSBitmapImageRep and draws into this
> newly allocated image.
>
> I subclass NSImage and add a few methods for drawing the picture.
> I've included 2 methods, the init and an example drawing method:
>
> ---8<-----8<-----8<-----
> - (id)initWithWidth:(int)width andHeight:(int)height
> {
>     NSSize        imageSize;
>     enum
>     {
>         kBitsPerSample        = 8,
>         kSamplesPerPixel        = 4,
>         kBytesPerPixel        = 4,
>         kBitsPerPixel            = kBytesPerPixel * 8,
>         kHasAlpha                = YES,
>         kIsPlanar                = NO
>     };
>
>     self = [super init];
>     if(self)
>     {
>         imageSize.width = (float) width;
>         imageSize.height = (float) height;
>         bitmapImageRep = [NSBitmapImageRep alloc];
>         [bitmapImageRep
>             initWithBitmapDataPlanes:NULL
>             pixelsWide:width
>             pixelsHigh:height
>             bitsPerSample:kBitsPerSample
>             samplesPerPixel:kSamplesPerPixel
>             hasAlpha:kHasAlpha
>             isPlanar:kIsPlanar
>             colorSpaceName:NSCalibratedRGBColorSpace
>             bytesPerRow:0
>             bitsPerPixel:kBitsPerPixel];
>
>         [self addRepresentation:bitmapImageRep];
>         [self setSize:imageSize];
>         [self setFlipped:YES];
>     }
>     return(self);
> }
>
> - (void)orPlotX:(long)xPos y:(long)yPos with:(long)pixel
> {
>     register long    x;
>     register long    y;
>     register long    width;
>
>     x = xPos;
>     y = yPos;
>     if(x >= 0 && y >= 0)
>     {
>         width = (int) [self size].width;
>         if(x < width)
>         {
>             if(y < (int) [self size].height)
>             {
>                 ((long *) [bitmapImageRep bitmapData])[y * width + x] |= pixel;
>             }
>         }
>     }
> }
> --->8----->8----->8-----
>
> Now, I use this line...
>     [offscreen compositeToPoint:NSZeroPoint fromRect:[self subImageRect]
> operation:NSCompositeCopy];
> ...to place it in the window.
>
> This all works very well if I set my screen depth to 32bit.
> If I switch to 16bit *after* the allocation or 8bit for that matter,
> it *still* works.
> Now... If I start the application in 16bit mode and switch to 32bit
> mode, nothing shows up.
> I've tried turning alpha on/off, and it seems there's no difference
> there.
>
> If I dump the NSBitmapImageRep info after the allocation, I get...
> bitsPerPixel:32
> bytesPerRow:404
> samplesPerPixel:4
> bytesPerPlane:32724
> isPlanar:0
> pixelsWide:101.000000
> pixelsHigh:81.000000
>
> which looks right in my eyes.
>
> Can anyone see what I'm doing wrong ?
> -Why does the image show up as black in 16bit color depth, when it's
> correct in 32bit color depth ?


Love,
Jens
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