//
// The multimedia graphics platform GLScene https://github.com/glscene
//

unit GLS.FilePNG;

(* PNG files loading implementation *)

interface

{$I GLScene.inc}

uses
  Winapi.OpenGL,
  System.Classes,
  System.SysUtils,
  VCL.Imaging.pngimage,

  GLS.OpenGLTokens,
  GLS.Strings,
  GLS.Context,
  GLS.Graphics,
  GLS.ApplicationFileIO,
  GLS.TextureFormat;

type

  TGLPNGImage = class(TGLBaseImage)
  private
  public
    class function Capabilities: TGLDataFileCapabilities; override;
    procedure LoadFromFile(const filename: string); override;
    procedure SaveToFile(const filename: string); override;
    procedure LoadFromStream(AStream: TStream); override;
    procedure SaveToStream(AStream: TStream); override;
    // Assigns from any Texture.
    procedure AssignFromTexture(textureContext: TGLContext;
      const textureHandle: Cardinal; textureTarget: TGLTextureTarget;
      const CurrentFormat: Boolean; const intFormat: TGLInternalFormat);
      reintroduce;
  end;

// --------------------------------------------------------------
implementation
// --------------------------------------------------------------

// ------------------
// ------------------ TGLPNGImage ------------------
// ------------------

procedure TGLPNGImage.LoadFromFile(const filename: string);
var
  fs: TStream;
begin
  if FileStreamExists(filename) then
  begin
    fs := TFileStream.Create(filename, fmOpenRead);
    try
      LoadFromStream(fs);
    finally
      fs.Free;
      ResourceName := filename;
    end;
  end
  else
    raise EInvalidRasterFile.CreateFmt('File %s not found', [filename]);
end;

procedure TGLPNGImage.SaveToFile(const filename: string);
var
  fs: TStream;
begin
  fs := TFileStream.Create(filename, fmOpenWrite or fmCreate);
  try
    SaveToStream(fs);
  finally
    fs.Free;
  end;
  ResourceName := filename;
end;

procedure TGLPNGImage.LoadFromStream(AStream: TStream);
var
  pngimage: TPngImage;
  rowBytes: Cardinal;
begin
  try
    pngimage := TPngImage.Create;
    pngimage.LoadFromStream(AStream);
    UpdateLevelsInfo;
    ReallocMem(fData, rowBytes * Cardinal(GetHeight));
  finally
    pngimage.Free;
  end;
end;

procedure TGLPNGImage.SaveToStream(AStream: TStream);
var
  pngimage: TPngImage;
begin
  try
    pngimage := TPngImage.Create;
    pngimage.SaveToStream(AStream);
  finally
    pngimage.Free;
  end;
end;

procedure TGLPNGImage.AssignFromTexture(textureContext: TGLContext;
  const textureHandle: Cardinal; textureTarget: TGLTextureTarget;
  const CurrentFormat: Boolean; const intFormat: TGLInternalFormat);
var
  oldContext: TGLContext;
  contextActivate: Boolean;
  texFormat: Cardinal;
  residentFormat: TGLInternalFormat;
  glTarget: Cardinal;
begin
  if not((textureTarget = ttTexture2D) or (textureTarget = ttTextureRect)) then
    Exit;
  oldContext := CurrentGLContext;
  contextActivate := (oldContext <> textureContext);
  if contextActivate then
  begin
    if Assigned(oldContext) then
      oldContext.Deactivate;
    textureContext.Activate;
  end;
  glTarget := DecodeTextureTarget(textureTarget);
  try
    textureContext.GLStates.TextureBinding[0, textureTarget] := textureHandle;
    fLevelCount := 0;
    fCubeMap := false;
    fTextureArray := false;
    // Check level existence
    gl.GetTexLevelParameteriv(glTarget, 0, GL_TEXTURE_INTERNAL_FORMAT,
      @texFormat);
    if texFormat > 1 then
    begin
      gl.GetTexLevelParameteriv(glTarget, 0, GL_TEXTURE_WIDTH, @FLOD[0].Width);
      gl.GetTexLevelParameteriv(glTarget, 0, GL_TEXTURE_HEIGHT,
        @FLOD[0].Height);
      FLOD[0].Depth := 0;
      residentFormat := OpenGLFormatToInternalFormat(texFormat);
      if CurrentFormat then
        fInternalFormat := residentFormat
      else
        fInternalFormat := intFormat;
      FindCompatibleDataFormat(fInternalFormat, fColorFormat, fDataType);
      Inc(fLevelCount);
    end;
    if fLevelCount > 0 then
    begin
      fElementSize := GetTextureElementSize(fColorFormat, fDataType);
      ReallocMem(fData, DataSize);
      gl.GetTexImage(glTarget, 0, fColorFormat, fDataType, fData);
    end
    else
      fLevelCount := 1;
    gl.CheckError;
  finally
    if contextActivate then
    begin
      textureContext.Deactivate;
      if Assigned(oldContext) then
        oldContext.Activate;
    end;
  end;
end;

class function TGLPNGImage.Capabilities: TGLDataFileCapabilities;
begin
  Result := [dfcRead, dfcWrite];
end;

// ---------------------------------------------------
initialization
// ---------------------------------------------------

RegisterRasterFormat('png', 'Portable Network Graphic', TGLPNGImage);

end.