BGRABitmap tutorial

[circular]

Which version of BGRABitmap are you using?

[Paul_]

Hi,

is there a simple solution how to change BGRABitmap contrast and brightness like in LazPaint  ( menu section: Colors - brightness / contrast) ?

[circular]

You can do the following:

Code: [Select]

procedure ChangeLightness(ABitmap: TBGRABitmap; AFactor, AShift: single);
var n: integer;
  p: PBGRAPixel;
  ec: TExpandedPixel;
  curLightness, newLightness: integer;
begin
  p := ABitmap.Data;
  for n := ABitmap.NbPixels-1 downto 0 do
  begin
    ec := GammaExpansion(p^);
    curLightness:= GetLightness(ec);
    newLightness:= round(curLightness*AFactor+AShift*65535);
    if newLightness > 65535 then newLightness:= 65535;
    ec := SetLightness(ec, newLightness, curLightness);
    p^ := GammaCompression(ec);
    inc(p);
  end;
end;

[Paul_]

Thank you, it looks good, only I can not go into black / dark.

What should be the range of AFactor and  AShift values ?

[circular]

With AFactor between 0 and 1, it becomes darker.

Note that if you would like to use a negative value for AShift, then the bounds would be ensured by adding a line:

Code: [Select]

if newLightness < 0 then newLightness := 0;

[Zittergie]

Hi,
I am replacing all my images (standard Timage) with bgrabitmaps. Standard Timages give problems on Ubuntu 14.x ARM , wrong or not rendering (giving message: Attempt to draw a drawable with depth 24 to a drawable with depth 32)

I would like to draw on the bitmap to show the anolog VU-meter:

VU-meter:

Code: [Select]

Form1.VuImage.Canvas.Pen.Color:=needle;
Form1.VuImage.Canvas.Pen.Width:=2;
Form1.VuImage.Canvas.Line(94, 94, y, z);
Spectrum Analyzer:

Code: [Select]

if VU_Settings.Active=3 then    // Spectrum Analyser
 begin
   If VU_Settings.Placement=2 then YAxes:= Form1.Panel_VU.Height div 2;
   If VU_Settings.Placement=3 then YAxes:= Form1.Panel_VU.Height-2;
   If VU_Settings.Placement=1 then YAxes:= 2;

   Form1.VuImage.Canvas.Pen.Width:=2;   Form1.VuImage.Canvas.Pen.Color:=clHighlight;
   Form1.VuImage.Canvas.Brush.Style:=bssolid; Form1.VuImage.Canvas.Brush.Color:=clBlack;
   Form1.VuImage.Canvas.Rectangle(0,0,Form1.Panel_VU.Width,Form1.Panel_VU.Height);
   For Counter:=0 to 117 do
   begin
    YValue:=round(MyThread.FFT[counter]*128); YValue2:=YValue;

    Form1.VuImage.Canvas.Pen.Color:=clLime;
    if VU_Settings.Placement=2 then
    begin
      if YValue>38 then YValue:=38;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes+YValue,round(2+counter*2),YAxes-YValue);
      if YValue2>60 then YValue2:=60;
      Form1.VuImage.Canvas.Pen.Color:=clGreen;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes+trunc(YValue2/1.8),2+counter*2,yAxes-trunc(YValue2/1.8));
      If VU_Settings.ShowPeaks then
      begin
        Form1.VuImage.Canvas.Pixels[Counter*2+2,YAxes-YValue]:=clRed;
        Form1.VuImage.Canvas.Pixels[Counter*2+3,YAxes-YValue]:=clRed;
      end;
    end;
   if VU_Settings.Placement=3 then
    begin
      if YValue>41 then YValue:=41;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes,2+counter*2,YAxes-round(YValue*1.8));
      if YValue2>60 then YValue2:=60;
      Form1.VuImage.Canvas.Pen.Color:=clGreen;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes,2+counter*2,yAxes-trunc(YValue2));
      If VU_Settings.ShowPeaks then
      begin
        Form1.VuImage.Canvas.Pixels[Counter*2+2,YAxes-round(YValue*1.8)]:=clRed;
        Form1.VuImage.Canvas.Pixels[Counter*2+3,YAxes-round(YValue*1.8)]:=clRed;
      end;
    end;
    if VU_Settings.Placement=1 then
    begin
      if YValue>40 then YValue:=40;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes,2+counter*2,YAxes+round(YValue*1.8));
      if YValue2>70 then YValue2:=70;
      Form1.VuImage.Canvas.Pen.Color:=clGreen;
      Form1.VuImage.Canvas.Line(2+counter*2,YAxes,2+counter*2,yAxes+trunc(YValue2));
      If VU_Settings.ShowPeaks then
      begin
        Form1.VuImage.Canvas.Pixels[Counter*2+2,YAxes+round(YValue*1.8)]:=clRed;
        Form1.VuImage.Canvas.Pixels[Counter*2+3,YAxes+round(YValue*1.8)]:=clRed;
      end;
    end;
   end;
 end;

I tried to translate it to use bgrabitmaps, but without success
Full source:  https://sourceforge.net/p/xixmusicplayer/svn/HEAD/tree/trunk/vuviewer.pas?format=raw

[lainz]

And how far you reached?

var
  Bitmap: TBGRABitmap;

Bitmap.Canvas --> here you have Canvas.
According to Circular is slower than using Bitmap.(DrawingMethodName) directly.

You need to do it line by line IMO. If you want to do it automatically use Bitmap.Canvas.

For example:
- Pen.Color, Pen.Width are not used in this way in BGRABitmap.

You must use DrawLineAntiAlias and specify parameters like Width and Color in the method directly.

To access pixels:
- There is a faster way that's used for example to make filters.

Code: [Select]

{
// all pixels //
var
  i: integer;
  p: PBGRAPixel;
begin
  p := Bitmap.Data;

  for i := Bitmap.NBPixels-1 downto 0 do
  begin
    p^.red := ;
    p^.green := ;
    p^.blue := ;
    p^.alpha := ;
    Inc(p);
  end;

// scan line //
var
  x, y: integer;
  p: PBGRAPixel;
begin
  for y := 0 to Bitmap.Height - 1 do
  begin
    p := Bitmap.Scanline[y];
    for x := 0 to Bitmap.Width - 1 do
    begin
      p^.red := ;
      p^.green := ;
      p^.blue := ;
      p^.alpha := ;
      Inc(p);
    end;
  end;
  Bitmap.InvalidateBitmap;
}
But you can also use Bitmap.Pixels[x,y]:= TBGRAPixel (like TColor with Alpha).

[aradeonas]

Zittergie I think you should make it a component from TBGRAVirtualScreen so its easier to control and for play and pause give it a active or pause property,For painting override RedrawBitmapContent like as I done it WallofCovers and paint what you want from the data that it can get from an Event when needed, so you have beautiful and easy to use component .
For painting as 008 said you should probably use TBGRABitmap functions for lines or gradient.

[circular]

There is an equivalent for Canvas, it is called CanvasBGRA and provides the same features as Canvas and supports antialiasing.

See : https://www.youtube.com/watch?v=HGYSLgtYx-U

[Carver413]

why do you have two canvas ?

[circular]

Because Canvas property gives access to the canvas of the system. It is the same as TBitmap.Canvas. There is not much control over how it renders things, it often does not support antialiasing and does not provide transparency. Also it is slower to use it because switching from direct pixel access to the system canvas need some intermediate processing.

CanvasBGRA property uses BGRABitmap functions, and thus provides antialiasing and transparency. It can be used along with direct pixel access without any restriction. So it generally better to use CanvasBGRA.

However, sometimes, it is necessary to use system functions, hence Canvas property is still here. Also it was here before and for backwards compatibility, it is still here.

[scons]

Is there a way to start drawing from the middlepoint of a TpaintBox ? To center a drawing ?

Edit: I've found it.