How can I disable interpolation on a GPU canvas FMX TImage or set interpolation to “nearest neighbor”

Question

I am trying to create a pinch-to-zoom TImage function and want to disable interpolation when resizing a firemonkey TImage control (and it needs to work across multiple devices).

Answer 1

Instead of using a TImage, you can paint directly the image on the canvas using a Texture

When you will create the texture you can assign it with GL_NEAREST instead of GL_LINEAR (IE: Texture.MagFilter)

Below the delphi function that will create the texture (for reference) :

class procedure TCustomContextOpenGL.DoInitializeTexture(const Texture: TTexture);
var
  Tex: GLuint;
begin
  if Valid then
  begin
    glActiveTexture(GL_TEXTURE0);
    glGenTextures(1, @Tex);
    glBindTexture(GL_TEXTURE_2D, Tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    case Texture.MagFilter of
      TTextureFilter.Nearest: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
      TTextureFilter.Linear: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    end;
    if TTextureStyle.MipMaps in Texture.Style then
    begin
      case Texture.MinFilter of
        TTextureFilter.Nearest: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
        TTextureFilter.Linear: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
      end;
    end
    else
    begin
      case Texture.MinFilter of
        TTextureFilter.Nearest: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        TTextureFilter.Linear: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      end;
    end;
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Texture.Width, Texture.Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, nil);
    glBindTexture(GL_TEXTURE_2D, 0);
    ITextureAccess(Texture).Handle := Tex;
    if (GLHasAnyErrors()) then
      RaiseContextExceptionFmt(@SCannotCreateTexture, [ClassName]);
  end;
end;