Copy an image

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mritter0
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Copy an image
I have loaded an image with this
  1. Object *
  2. LoadInternalImage(STRPTR Render)
  3. {
  4. return(IIntuition->NewObject(BitMapClass,NULL,
  5. BITMAP_SourceFile, Render,
  6. BITMAP_Screen, DefaultPubScreen,
  7. BITMAP_Precision, PRECISION_EXACT,
  8. BITMAP_Masking, TRUE,
  9. TAG_DONE));
  10. }
Now I am trying to make a copy of it to keep the original and do some modifying to the copy. Everything I have tried loses the alpha transparency and it shows up pink. The image body is fine.
  1. Object *
  2. CopyImage(Object *SourceImg)
  3. {
  4. Object *Img;
  5. struct BitMap *SourceBM, *DestBM;
  6. uint32 Width, Height, Depth, PixelFormat;
  7.  
  8. if (SourceImg==NULL)
  9. return(NULL);
  10.  
  11. IIntuition->GetAttrs(SourceImg,
  12. BITMAP_BitMap, &SourceBM,
  13. TAG_DONE);
  14.  
  15. Width=IGraphics->GetBitMapAttr(SourceBM,BMA_WIDTH);
  16. Height=IGraphics->GetBitMapAttr(SourceBM,BMA_HEIGHT);
  17. Depth=IGraphics->GetBitMapAttr(SourceBM,BMA_DEPTH);
  18. // Depth=IGraphics->GetBitMapAttr(SourceBM,BMA_BITSPERPIXEL);
  19. PixelFormat=IGraphics->GetBitMapAttr(SourceBM,BMA_PIXELFORMAT);
  20.  
  21. // I am forcing it to this format. Either way has same result.
  22. if (!(DestBM=IGraphics->AllocBitMapTags(Width,Height,32,//Depth,
  23. BMATags_PixelFormat, PIXF_A8R8G8B8,//PixelFormat,
  24. BMATags_Clear, TRUE,
  25. BMATags_Displayable, TRUE,
  26. TAG_DONE)))
  27. {
  28. return(NULL);
  29. }
  30.  
  31. // I have tried every combination, plus others.
  32. if (IGraphics->CompositeTags(
  33. COMPOSITE_Src, SourceBM, DestBM,
  34. // COMPOSITE_Src_Over_Dest, SourceBM, DestBM,
  35. // COMPTAG_Flags, COMPFLAG_IgnoreDestAlpha,
  36. // COMPTAG_Flags, COMPFLAG_SrcAlphaOverride | COMPFLAG_IgnoreDestAlpha,
  37. // COMPTAG_Flags, COMPFLAG_SrcAlphaOverride,
  38. TAG_DONE) != COMPERR_Success)
  39. {
  40. IGraphics->FreeBitMap(DestBM);
  41.  
  42. return(NULL);
  43. }
  44.  
  45. if (!(Img=IIntuition->NewObject(BitMapClass,NULL,
  46. BITMAP_BitMap, DestBM,
  47. BITMAP_Width, Width,
  48. BITMAP_Height, Height,
  49. BITMAP_HasAlpha, TRUE,
  50. BITMAP_Screen, DefaultPubScreen,
  51. BITMAP_Precision, PRECISION_EXACT,
  52. BITMAP_Masking, TRUE,
  53. TAG_DONE)))
  54. {
  55. IGraphics->FreeBitMap(DestBM);
  56.  
  57. return(NULL);
  58. }
  59.  
  60. return(Img);
  61. }
What is happening to the transparency? The original image displays just fine, the copy does not (pink).
broadblues
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Re: Copy an image
The problem is the probably Composite call. CompoisteTags does a composite operation not a copy. Thus the alpha channel is not preserved, rather it's used to control the composite. A few people have been caught out by this. It's not obvious to me what specific change you are trying to make with the Composite operation?
mritter0
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Re: Copy an image
That's the weird thing: CompositeTags() does "save" the alpha channel when loaded from a datatype. I use it a lot in my program. I load a BitMapClass with BITMAP_Render,"path", and such; AllocBitMapTags() a new bitmap; lock it and IDoMethod() pdtBlitPixelArrayBuffer to it, unlock it; AllocBitMapTags() another bitmap (destination); CompositeTags() with a scale down; create BitMapClass with destination bitmap and all it good. I have tried with a mix and match of these tags with no luck, or worse results:
  1. COMPTAG_Flags, COMPFLAG_IgnoreDestAlpha,
  2. COMPTAG_Flags, COMPFLAG_SrcAlphaOverride | COMPFLAG_IgnoreDestAlpha,
  3. COMPTAG_Flags, COMPFLAG_SrcAlphaOverride,
But above I have already loaded the image to a BitMapClass and am copying the BITMAP_BitMap from it and the transparency gets lost; end up violet. I am using CompositeTags() because I may need to scale it, so just have it ready to go (currently just copying it). I also tried to use BltBitMapTags() but has the same result: alpha is violet.
  1. IGraphics->BltBitMapTags(
  2. BLITA_Source, SourceBM,
  3. BLITA_Dest, DestBM,
  4. BLITA_SrcType, BLITT_BITMAP,
  5. BLITA_DestType, BLITT_BITMAP,
  6. BLITA_Width, Width,
  7. BLITA_Height, Height,
  8. BLITA_UseSrcAlpha, TRUE,
  9. TAG_DONE);
So I would say it has something to do with the way GetAttrs() BITMAP_BitMap is getting the data, losing the alpha data along the way. ??????
broadblues
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Re: Copy an image
BLITA_UseSrcAlpha, TRUE, will alpha blend the src with the destination, that *will* lose the alpha component of the src, you want a straight copy with no blending. But I have to say your approach is wrong. bitmap.image is not for loading images but displaying them (naturally it supports loading too, as a convenience). If you want to load an image them modify it, use the datatype directly, then extact the 32bit bitmap, modify as required and create your new bitmap.image from it.
mritter0
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Re: Copy an image
I hear what you are saying about using datatypes to load the image, will try that later. For now, I I found another way to do what I need. I still need/want to get the copy to work, not giving up on it.
mritter0
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Re: Copy an image
I used the "traditional" method of loading the image with datatypes and BltBitMapTags(), got success.
hypex
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Joined: 2011-09-09 16:20
Re: Copy an image
Just out of interest, did you also try copying the bitmap by grabbing a pointer to it and passing that along with BITMAP_BitMap as the source instead? Thus avoiding all the duplicating you were doing. If that could work.
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