TFPMemoryImage assigned to TImage.Picture don't displaying
lazarus / 39-Graphics

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Awkward · 2021-09-09 21:35

I use next function to show picture file from memory. It can work for
JPG or PNG but not DDS. if i will uncomment "SaveToFile" line, i will
get proper PNG file. but impgPreview (TImage control) after assigning
still empty. What i doing wrong?

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TRGGUIForm.PreviewImage(const aname:string);var  limg:TFPMemoryImage; 
lstr:TMemoryStream;  lfpc:TFPColor;  ldata:PByte; 
lidx,y,x,lsize,lheight,lwidth:integer;begin  if
ExtractFileExt(aname)='.DDS' then  begin   
LoadDDSImage(FUData,MemSize(FUData),ldata,lwidth,lheight);    
limg:=TFPMemoryImage.Create(lwidth,lheight);    lidx:=0;    for y:=0
to lheight-1 do    begin      for x:=0 to lwidth-1 do      begin     
 lfpc.Red  :=ldata[lidx+0] shl 8;        lfpc.Green:=ldata[lidx+1] shl
8;        lfpc.Blue :=ldata[lidx+2] shl 8;       
lfpc.Alpha:=ldata[lidx+3];        limg.Colors[x,y]:=lfpc;       
inc(lidx,4);      end;    end;    FreeMem(ldata);{  if i will use next
2 lines, picture displaying    limg.SaveToFile('d:\112.png');   
imgPreview.Picture.LoadFromFile('d:\112.png');}   
imgPreview.Picture.Assign(limg);    limg.Free;  end  else  begin   
lstr:=TMemoryStream.Create();    try      lstr.SetBuffer(FUData);    
imgPreview.Picture.LoadFromStream(lstr);    finally      lstr.Free;  
end;  end;  imgPreview.Visible:=true;end;

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Remy Lebeau · 2021-09-09 22:11

Quote from: Awkward on September 09, 2021, 11:35:07 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i {  if i
will use next 2 lines, picture displaying   
limg.SaveToFile('d:\112.png');   
imgPreview.Picture.LoadFromFile('d:\112.png');}
Have you tried using limg.SaveToStream() followed by
imgPreview.Picture.LoadFromStream()?  You should not need to use a
temp file at all, but you do need to still pick an image format (JPG,
PNG, etc) for the TFPMemoryImage data to be converted to for display.

Try this:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TRGGUIForm.PreviewImage(const aName: string);var  limg:
TFPMemoryImage;  lstr: TMemoryStream;  lfpc: TFPColor;  ldata: PByte; 
lidx, y, x, lsize, lheight, lwidth: Integer;  lwriter:
TFPWriterPNG;begin  if ExtractFileExt(aName) = '.DDS' then  begin   
LoadDDSImage(FUData, MemSize(FUData), ldata, lwidth, lheight);    try 
    limg := TFPMemoryImage.Create(lwidth, lheight);      try       
lidx := 0;        for y := 0 to lheight-1 do        begin          for
x := 0 to lwidth-1 do          begin            lfpc.Red :=
ldata[lidx+0] shl 8;            lfpc.Green := ldata[lidx+1] shl 8;   
       lfpc.Blue := ldata[lidx+2] shl 8;            lfpc.Alpha :=
ldata[lidx+3];            limg.Colors[x, y] := lfpc;           
Inc(lidx, 4);          end;        end;        FreeMem(ldata);       
ldata := nil;        lstr := TMemoryStream.Create;        try        
lwriter := TFPWriterPNG.Create;          try           
limg.SaveToStream(lstr, lwriter);            // or:
lwriter.ImageWrite(lstr, limg);          finally           
lwriter.Free;          end;          lstr.Position := 0;         
imgPreview.Picture.LoadFromStream(lstr);        finally         
lstr.Free;        end;      finally        limg.Free;      end;   
finally      if ldata <> nil then        FreeMem(ldata);    end;  end 
else  begin    lstr := TMemoryStream.Create;    try     
lstr.SetBuffer(FUData);      imgPreview.Picture.LoadFromStream(lstr); 
  finally      lstr.Free;    end;  end;  imgPreview.Visible :=
true;end;

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Awkward · 2021-09-10 06:23

i know this method, didn't tried it (and i think, it will work). But i
wandered and want to know, why direct assign don't work.

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wp · 2021-09-10 09:05

Not 100% sure, but AFAIK TFPMemoryImage only provides a buffer for the
image, but no information how the data in the buffer will have to be
organized in the destination image format.

I'd use a TLazIntfImage instead which provides a simpler interface to
the classes of the graphics units. A png image, for example, can
loaded from a LazIntfImage and thus set its required memory layout.

Untested:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
IntfGraphics, fpimage; procedure TForm1.Button1Click(Sender:
TObject);var  img: TLazIntfImage;  png: TCustomBitmap;  lHeight,
lWidth: Integer;  lData: PByte;begin  LoadDDSImage(FUData,
MemSize(FUData), ldata, lwidth, lheight);  try    png :=
TPortableNetworkgraphic.Create; // or TJpegImage.Create, or
TBitmap.Create, or ...    try      png.SetSize(lWidth, lHeight);     
png.PixelFormat := pf32bit;      img := png.CreateIntfImage;      try 
      for y := 0 to lheight-1 do        begin          for x := 0 to
lwidth-1 do          begin            lfpc.Red := ldata[lidx+0] shl
8;            lfpc.Green := ldata[lidx+1] shl 8;            lfpc.Blue
:= ldata[lidx+2] shl 8;            lfpc.Alpha := ldata[lidx+3];      
    limg.Colors[x, y] := lfpc;            Inc(lidx, 4);          end; 
      end;        png.LoadFromIntfImage(img);       
imgPreview.Picture.Assign(png);      finally        img.Free;     
end;    finally      png.Free;    end;  finally    FreeMem(lData); 
end;end;

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Awkward · 2021-09-11 16:25

Quote from: wp on September 10, 2021, 11:05:20 amNot 100% sure, but
AFAIK TFPMemoryImage only provides a buffer for the image, but no
information how the data in the buffer will have to be organized in
the destination image format.

I'd use a TLazIntfImage instead which provides a simpler interface to
the classes of the graphics units. A png image, for example, can
loaded from a LazIntfImage and thus set its required memory layout.

you forgot to rename "limg" to "img" at one place and initialize
"lidx" by 0 at another.
well, picture displayed but on plack background (like no alpha)

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wp · 2021-09-11 17:57

Since I don't have neither your LoadDDSImage procedure nor a DDS image
for testing, I simulated the procedure by the Lazarus paw which is
read into a png, and I use the IntfImage to color the black paw in red
and replace the alpha-channel by a gradient from fully transparent at
the left to fully opaque white at the right. Look at the attached
demo. It works as expected.

If this basic code does not work in your example you should check
whether the color and alpha channels are handled correctly. FPImage
uses 16-bit colors and alpha. This is why you shl the rgb value by 8
bits. But you do not shl the alpha channel. I do not know if this
explains why your image background is black.