How to create and return PNG image using HTTP-server?
lazarus / 38-Networking and Web Programming

----------------------------------------------------------------------
artem101 · 2020-12-26 14:49

Is there an example how to draw and return PNG image using fpWeb
module?
Thanks.

----------------------------------------------------------------------
lucamar · 2020-12-26 15:02

There might be but I don't know of any. However, it shouldn't be too
difficult: use a TPicture or directly a TPortableNetworkGraphic to
draw whatever you need, save it to a file/stream and make the server
return that file/stream.

You could even transfer directly the TPicture/TPortableNetworkGraphic 
to the Response.ContentStream using SaveToStream, avoiding all
iteraction with the disk (other than OS swapping, o.c.)

Edit: Replaced TPNGImage by TPortableNetworkGraphic

----------------------------------------------------------------------
artem101 · 2020-12-26 15:37

I make this code, but it doesn`t work:
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
TFPWebModule1.DataModuleRequest(Sender: TObject; ARequest: TRequest; 
AResponse: TResponse; var Handled: Boolean);const  WIDTH = 256; 
HEIGHT = 256;var  str: String;  img: TPortableNetworkGraphic; 
textWidth, textHeight: integer;  memStrm: TMemoryStream;begin 
//WriteLn('Url: ', ARequest.URI);  //WriteLn('Args: ',
ARequest.QueryFields.Text);   with ARequest.QueryFields do    str :=
Format('x=%s y=%s z=%s', [Values['x'], Values['y'], Values['z']]);   
img := TPortableNetworkGraphic.Create;  memStrm :=
TMemoryStream.Create;  try    // Create image    img.SetSize(WIDTH,
HEIGHT);     img.Canvas.Font.Color:=clRed;   
img.Canvas.GetTextSize(str, textWidth, textHeight);   
img.Canvas.TextOut((WIDTH - textWidth) div 2, (HEIGHT - textHeight)
div 2, str);     // Send image to output stream   
img.SaveToStream(memStrm);   
AResponse.ContentStream.CopyFrom(memStrm, memStrm.Size);   
AResponse.ContentStream.Position:=0;    AResponse.WriteContent; 
finally    img.Free;    AResponse.ContentStream:=nil;   
memStrm.Free;  end;   AResponse.Code:=200; 
AResponse.ContentType:='image/png';  Handled:=true;end; 
First problem:
Quoteunit1.pas(64,15) Error: identifier idents no member
"WriteContent"
After I commented line 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 AResponse.WriteContent; server started to work, but second
problem appeared
https://ibb.co/6gbHSn5
at line
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
img.SetSize(WIDTH, HEIGHT);