Re: Rendering grayscale on opengl using nsbitmaprep

[Indie AN]

Hi,
 I had attached the image along this  mail.  Its  part of
cocos2d-iphone project
(https://github.com/ANindie/cocos2d-GNUstep/raw/1219df69bd64feb6aa2ae83073e1f9e380e6f9ad/src/Resources/Images/stars2-grayscale.png).
  As per 'Gimp 'it contains 2 channels, alpha and luminosity. 64*64 pixels.
GNUstep NSBitmapimagerep reports that samplesPerPixel=2,
BytesPerRow=128. So I tried to use the data provided by
NSBitmapimagerep  to generate RBGA pixel data. Either my approach
going wrong or NSBitmapimagerep doesn't  give proper data.
 Also I tried rendering image assuming BytesPerRow = 64*4 half of the
image renders properly rest is black/garbage.


On 2/12/11, Gregory Casamento <greg.casamento@gmail.com> wrote:
> Which image?  I don't see an attachment or a link.
>
> On Thursday, February 10, 2011, indieAN <an.indian.indie@gmail.com> wrote:
>> Hi,
>>   I trying to render a gray scale image (contains 2 channels luminosity
>> and alpha) using opengl. Actually this image is a png image. I am
>> decoding it using nsbitmaprep. But only garbage  gets rendered. Can any
>> body tell whats wrong with following code. Or their is bug in
>> nsbitmapImagerep for rendering grayscale?
>>
>>
>> -(id) initPremultipliedATextureWithBitmap:(NSBitmapImageRep*)bitmap
>> pixelsWide:(NSUInteger)POTWide pixelsHigh:(NSUInteger)POTHigh
>> {
>>
>>     short bytesPerPixel = [bitmap bitsPerPixel]>>3;//2
>>         unsigned char * data = calloc(1, POTHigh  * POTWide * 4);
>>         const unsigned char * originaldata = [bitmap bitmapData];
>>
>>
>>
>>     NSSize size=NSMakeSize([bitmap pixelsWide],[bitmap
>> pixelsHigh]); //64*64
>>     NSUInteger bytesPerRow = [bitmap bytesPerRow];//128
>>     NSUInteger pixelPerRow =  bytesPerRow / bytesPerPixel;//64
>>     CCTexture2DPixelFormat      pixelFormat;
>>
>>     NSUInteger inputPixelPerRow = POTWide * 4;
>>
>>
>>
>>      int spp = [bitmap samplesPerPixel];  //2
>>
>>
>> #define FLIPPED_BITMAP 0
>>      int i;
>>
>>      for (i = 0; i < size.height ; i++)
>>     {
>>
>>
>> #if FLIPPED_BITMAP
>>      int vrow=(int)size.height -i-1;
>> #else
>>      int vrow=i;
>> #endif
>>
>>
>>       if(spp == 2)
>>       {
>>
>>
>>         unsigned char * dest =  data + (vrow * POTWide * 4);
>>         const unsigned char * src =  originaldata + (i * bytesPerRow);
>>
>>         int k=0;
>>         for(k=0; k<size.width ; k++)
>>         {
>>
>>                 *(dest +k*4+3)=*(src+k*2+1); //alpha
>>
>>                  *(dest +k*4) = *(src+k*2+2);//r
>>                  *(dest +k*4 + 1) = *(src+k*2);//g
>>                  *(dest +k*4 + 2) = *(src+k*2);//b
>>
>>         }
>>       }
>>        else
>>        memcpy(data + (vrow * POTWide * 4), originaldata + (i *
>> bytesPerRow), bytesPerRow);
>>    }
>>
>>
>>
>>         self = [self initWithData:data pixelFormat:pixelFormat
>> pixelsWide:POTWide pixelsHigh:POTHigh contentSize:size
>>                         unpackRowLength:POTWide];
>>
>>
>>         return self;
>> };
>>
>> Thanks in advance.
>> -indieAN
>> https://github.com/ANindie/cocos2d-GNUstep
>>
>>
>>
>> _______________________________________________
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>> Discuss-gnustep@gnu.org
>> http://lists.gnu.org/mailman/listinfo/discuss-gnustep
>>
>
> --
> Gregory Casamento - GNUstep Lead/Principal Consultant, OLC, Inc.
> yahoo/skype: greg_casamento, aol: gjcasa
> (240)274-9630 (Cell)
>

stars2-grayscale.png
Description: PNG image