TPNGObject - Create a new blank image and draw translucent images on it - delphi

I am building an application that has "virtual windows". The output is TImage object.
1) The application loads window skin files into TPNGObject's:
2) Then application has to create a new blank TPNGObject, and resize the skin files to needed sizes and draw them on that blank image. Should look something like this:
3) And the final output on TImage:
The problem is that I do know how to create a completely blank off screen image. Of course I could simply render the skin files on to TImage each time, but it's easier and better to resize skin files and create the window once, instead.
I'm using the PNG Library by Gustavo Daud, version 1.564 (31st July, 2006).

The below uses CreatePNG procedure of 'pngfunctions.pas' of Martijn Sally, from an extension library (pngcomponents) to pngimage.
var
Bmp, Mask: TBitmap;
PNG: TPNGObject;
begin
Bmp := TBitmap.Create;
Bmp.PixelFormat := pf24bit;
Bmp.SetSize(64, 64);
Bmp.Canvas.Brush.Color := clBtnFace;
Bmp.Canvas.Font.Color := clRed;
Bmp.Canvas.Font.Size := 24;
Bmp.Canvas.TextOut(4, 10, 'text');
Mask := TBitmap.Create;
Mask.PixelFormat := pf24bit;
Mask.Canvas.Brush.Color := clBlack;
Mask.SetSize(64, 64);
Mask.Canvas.Font.Color := clWhite;
Mask.Canvas.Font.Size := 24;
Mask.Canvas.TextOut(4, 10, 'text');
PNG := TPNGObject.Create;
CreatePNG(Bmp, Mask, PNG, False);
PNG.Draw(Canvas, Rect(10, 10, 74, 74));
// finally, free etc...
Here's the output (black, white squares are TShapes):

My other answer is another alternative which I suggest. However your question still poses an issue: The PNG library must either have a bug which is preventing any canvas drawing from being visible (after using CreateBlank constructor with COLOR_RGBALPHA as color type) or we're all missing something.
It looks like the only workaround that I can see is (as you mention in your edit) use a Bitmap to do your drawing instead. Use the transparent properties of this bitmap (Transparent: Bool and TransparentColor: TColor) to set up the transparent area of your image, then when you need a transparent PNG, just copy that bitmap over to the new PNG object...
BMP.Width:= 100;
BMP.Height:= 100;
BMP.Transparent:= True;
BMP.TransparentColor:= clWhite;
BMP.Canvas.Brush.Style:= bsSolid;
BMP.Canvas.Brush.Color:= clWhite;
BMP.Canvas.FillRect(BMP.Canvas.ClipRect);
BMP.Canvas.Brush.Color:= clBlue;
BMP.Canvas.Ellipse(10, 10, 90, 90);
PNG.Assign(BMP);
And the white area of the image should be transparent. There are other ways of accomplishing the transparent area, but that's another subject.
Image:
Is this what you're trying to do?

I apologize to people that I messed their heads up.
It turns out CreateBlank works as wanted. The problem was that I was drawing PNG on PNG canvas (PNG.Canvas.Draw). Canvas doesn't really support transparency. To draw a translucent PNG on another PNG you will need a procedure/function that merges those both layers together. With some googling I ended up with this procedure:
procedure MergePNGLayer(Layer1, Layer2: TPNGObject; Const aLeft, aTop: Integer);
var
x, y: Integer;
SL1, SL2, SLBlended: pRGBLine;
aSL1, aSL2, aSLBlended: PByteArray;
blendCoeff: single;
blendedPNG, Lay2buff: TPNGObject;
begin
blendedPNG := TPNGObject.Create;
blendedPNG.Assign(Layer1);
Lay2buff:=TPNGObject.Create;
Lay2buff.Assign(Layer2);
SetPNGCanvasSize(Layer2, Layer1.Width, Layer1.Height, aLeft, aTop);
for y := 0 to Layer1.Height - 1 do
begin
SL1 := Layer1.Scanline[y];
SL2 := Layer2.Scanline[y];
aSL1 := Layer1.AlphaScanline[y];
aSL2 := Layer2.AlphaScanline[y];
SLBlended := blendedPNG.Scanline[y];
aSLBlended := blendedPNG.AlphaScanline[y];
for x := 0 to Layer1.Width - 1 do
begin
blendCoeff:=aSL1[x] * 100/255/100;
aSLBlended[x] := round(aSL2[x] + (aSL1[x]-aSL2[x]) * blendCoeff);
SLBlended[x].rgbtRed := round(SL2[x].rgbtRed + (SL1[x].rgbtRed-SL2[x].rgbtRed) * blendCoeff);
SLBlended[x].rgbtGreen := round(SL2[x].rgbtGreen + (SL1[x].rgbtGreen-SL2[x].rgbtGreen) * blendCoeff);
SLBlended[x].rgbtBlue := round(SL2[x].rgbtBlue + (SL1[x].rgbtBlue-SL2[x].rgbtBlue) * blendCoeff);
end;
end;
Layer1.Assign(blendedPNG);
Layer2.Assign(Lay2buff);
blendedPNG.Free;
Lay2buff.Free;
end;
Usage:
var
PNG1, PNG2: TPNGObject;
begin
PNG1 := TPNGObject.CreateBlank(COLOR_RGBALPHA, 16, 500, 500);
PNG2 := TPNGObject.Create;
PNG2.LoadFromFile('...*.png');
MergePNGLayer(PNG1, PNG2, 0, 0);
// PNG1 is the output
And again, I am really sorry to users that wanted to help, but couldn't due to not understanding me.

I don't have answer to this question but I figured out how to get same result with any PNG editor. I have created blank 1000x1000 PNG image and saved it in my application directory. Then I open this image in my program and resize image to needed sizes (smaller of course) and that's the trick.

Related

How to use correctly TBitmap object to save a file with transparency?

Below is my sample code:
var lBitmap: TBitmap;
begin
lBitmap := TBitmap.Create;
lBitmap.PixelFormat := TPixelFormat.pf32bit;
lBitmap.Transparent := TRUE; // !
lBitmap.LoadFromFile( 'd:\temp\bmp32b_300dpi_transparent_400x250.bmp' );
// Bitmap RGB+Alpha created with GIMP
// modifications on pixels
Canvas.Draw(100, 0, lBitmap);
// Up to this point it is correct, the drawing is painted with transparency
lBitmap.SaveToFile( 'd:\tmp\after.bmp' ); // after this -> I have lost transparency
lBitmap.Free;
end;
How to use correctly TBitmap object to save a file with transparency?
It seems to me like TBitmap doesn't support saving bitmaps with alpha channels. And maybe we shouldn't blame the VCL for this, because BMPs with alpha transparency are uncommon. Many applications don't support transparent BMPs.
This being said, I "reverse-engineered" a BMP with alpha channel created in GIMP and wrote the following Delphi routine to produce the very same bitmap:
procedure SaveTransparentBitmap(ABitmap: TBitmap; const AFileName: string);
var
FS: TFileStream;
BFH: TBitmapFileHeader;
BIH: TBitmapV5Header;
y: Integer;
sl: PUInt64;
begin
// ABitmap MUST have the GIMP BGRA format.
FS := TFileStream.Create(AFileName, fmOpenWrite);
try
// Bitmap file header
FillChar(BFH, SizeOf(BFH), 0);
BFH.bfType := $4D42; // BM
BFH.bfSize := 4 * ABitmap.Width * ABitmap.Height + SizeOf(BFH) + SizeOf(BIH);
BFH.bfOffBits := SizeOf(BFH) + SizeOf(BIH);
FS.Write(BFH, SizeOf(BFH));
// Bitmap info header
FillChar(BIH, SizeOf(BIH), 0);
BIH.bV5Size := SizeOf(BIH);
BIH.bV5Width := ABitmap.Width;
BIH.bV5Height := ABitmap.Height;
BIH.bV5Planes := 1;
BIH.bV5BitCount := 32;
BIH.bV5Compression := BI_BITFIELDS;
BIH.bV5SizeImage := 4 * ABitmap.Width * ABitmap.Height;
BIH.bV5XPelsPerMeter := 11811;
BIH.bV5YPelsPerMeter := 11811;
BIH.bV5ClrUsed := 0;
BIH.bV5ClrImportant := 0;
BIH.bV5RedMask := $00FF0000;
BIH.bV5GreenMask := $0000FF00;
BIH.bV5BlueMask := $000000FF;
BIH.bV5AlphaMask := $FF000000;
BIH.bV5CSType := $73524742; // BGRs
BIH.bV5Intent := LCS_GM_GRAPHICS;
FS.Write(BIH, SizeOf(BIH));
// Pixels
for y := ABitmap.Height - 1 downto 0 do
begin
sl := ABitmap.ScanLine[y];
FS.Write(sl^, 4 * ABitmap.Width);
end;
finally
FS.Free;
end;
end;
This write a BITMAPFILEHEADER followed by a BITMAPV5HEADER and the pixel data in BGRA format.
I omit all kinds of error checking. For instance, I don't verify that ABitmap actually has the required format.
Test:
procedure TForm1.FormCreate(Sender: TObject);
var
bm: TBitmap;
begin
bm := TBitmap.Create;
try
bm.LoadFromFile('C:\Users\Andreas Rejbrand\Desktop\Test.bmp');
SaveTransparentBitmap(bm, 'C:\Users\Andreas Rejbrand\Desktop\Test2.bmp');
finally
bm.Free;
end;
end;
After this, Test.bmp and Test2.bmp are binary equal.
Saving 32-bit bitmaps with alpha channels needs a workaround as #Andreas Rejbrand has pointed out. There also seems to be some more confusion about the BMP file format, what the TBitmap.Transparent property does, and how you draw bitmaps transparently with the VCL.
32-bit bitmaps are the only bitmaps that carry information about transparency in the files. They have that information in the alpha channel and nowhere else. In the alpha channel, every pixel has its own 0-255 alpha value in the RGBA structure. This is often referred to as partial transparency.
When you draw/display 32-bit bitmaps, you have to pay attention to the TBitmap.AlphaFormat property. It defaults to afIgnore, which means that the bitmap is drawn without transparency. Use afPremultiplied or afDefined to draw with transparency. The latter is probably what you want.
The TBitmap.Transparent property is specific to the VCL TBitmap, and there is nothing in the BMP file format that corresponds to it. It's just a simple way to display bitmaps transparently, where a color defines which pixels should be fully transparent. The application must be familiar with the bitmaps to be able to use this method. It's also important to be aware of how the TBitmap.TransparentMode property works. It defaults to tmAuto, which sets the color of the bottom-leftmost pixel of the bitmap as TBitmap.TransparentColor. When TransparentMode is set to tmFixed, the TBitmap.TransparentColor you have specified is used. This method can also be used on 32-bit bitmaps.
Note that when you draw with the standard VCL TCanvas drawing routines on a 32-bit bitmap with transparency in the alpha channel, the transparency will be lost where you have drawn.
It seems that in your sample code, you have ignored AlphaFormat and TransparentMode. You should also decide if you want to use the transparency in the alpha channel or the TBitmap.Transparent method. But we have no bitmap in order to check if that is the real problem.

Transparent PNG image loaded from resource file, resized with Grapics32 and drawn on the Canvas

I need a little help...
I have a transparent PNG image in my application resources. Until now I was loading it in a TPngImage and draw it on the screen with Canvas.Draw(X, Y, PngImage);. And it was drawn transparently. Now I updated my application to be DpiAware and I need to scale all images. I need a quality resampler and I choose to use Graphics32. I managed to do the resampling but I don't know how to keep the transparecy... I try all that I cand think of... The result of the following code is the image drawn with black color in the transparent region...
Foto32, Buff: TBitmap32;
FotoPng: TPngImage;
constructor TForm.Create(AOwner: TComponent);
const BkgHeight = 380;
var Res: TKernelResampler;
SRect, DRect: TRect;
ImgWidth: Integer;
begin
inherited;
Buff:= TBitmap32.Create;
Res:= TKernelResampler.Create;
Res.Kernel:= TLanczosKernel.Create;
FotoPng:= TPngImage.Create;
FotoPng.Transparent:= True;
FotoPng.TransparentColor:= clBlack;
FotoPng.LoadFromResourceName(HInstance, 'BKG_FOTO');
Foto32:= TBitmap32.Create;
Foto32.DrawMode:= dmBlend;
Foto32.CombineMode:= cmMerge;
Foto32.OuterColor:= clBlack;
Foto32.Canvas.Brush.Style:= bsClear;
Foto32.SetSize(FotoPng.Width, FotoPng.Height);
FotoPng.Draw(Foto32.Canvas, Rect(0, 0, FotoPng.Width, FotoPng.Height));
ImgWidth:= Round(Real(Foto32.Width / Foto32.Height) * BkgHeight);
SRect:= Rect(0, 0, Foto32.Width, Foto32.Height);
Buff.DrawMode:= dmBlend;
Buff.CombineMode:= cmMerge;
Buff.OuterColor:= clBlack;
Buff.Canvas.Brush.Style:= bsClear;
Buff.SetSize(Scale(ImgWidth), Scale(BkgHeight));
DRect:= Rect(0, 0, Buff.Width, Buff.Height);
Res.Resample(Buff, DRect, DRect, Foto32, SRect, dmTransparent {dmBlend}, nil);
end;
procedure TForm.Paint;
begin
// ....
Buff.DrawTo(Canvas.Handle, X, Y);
end;
And this is my transparent PNG image compiled into resources:
https://postimg.cc/3yy3wrJB
I found here a similar question, but I don't use the image with a TImage, I draw it directly on the canvas. And in the single answer, David says:
Anyway, if that is so, I would combine the transparency support of
TImage with the re-sampling ability of TBitmap32 to build a solution
that way. Keep the original image in a TBitmap32 instance. Whenever
you need to load it into the TImage component, for example when
re-sizing, use TBitmap32 to perform an in-memory re-size and load that
re-sized image.
This is exactly what I'm trying to do, but I don't know why the transparecy is not working. Any ideas ?
Your issue seems to be an issue with drawing the Buffer to the screen. Bitmap32 uses StretchDIBits for painting which ignores the alpha channel.
You could use the AlphaBlend function in order to draw your image:
procedure TForm1.FormPaint(Sender: TObject);
var
BF: TBlendFunction;
begin
BF.BlendOp := AC_SRC_OVER;
BF.BlendFlags := 0;
BF.SourceConstantAlpha := 255;
BF.AlphaFormat := AC_SRC_ALPHA;
Winapi.Windows.AlphaBlend(Canvas.Handle, 0, 0, Buff.Width, Buff.Height,
Buff.Canvas.Handle, 0, 0, Buff.Width, Buff.Height, BF);
end;
Or convert your TBitmap32 to a Delphi TBitmap and paint that using the VCL:
procedure TForm1.FormPaint(Sender: TObject);
var
Bmp: TBitmap;
I: Integer;
begin
Bmp := TBitmap.Create;
try
Bmp.PixelFormat := pf32bit;
Bmp.AlphaFormat := afDefined;
Bmp.SetSize(Buff.Width, Buff.Height);
for I := 0 to Buff.Height - 1 do
Move(Buff.ScanLine[I]^, Bmp.ScanLine[I]^, Buff.Width * 4);
Canvas.Draw(0, 0, Bmp);
finally
Bmp.Free;
end;
end;

Saving transparent (alpha channel) PNG from TImageList

I have a TImageList which contains transparent icons (32bit, with alpha channel). What I want to do is to save individual icons based on image index as PNG file(s), while preserving alpha channel transparency. Using RAD Studio 2010 so it has TPngImage support, no need for third party libraries. Images are loaded into TImageList from PNG "sprite" image using the method here - Add a png image to a imagelist in runtime using Delphi XE - so the transparency is preserved upon loading. Now I need to save them out individually, in other words, extract individual images from sprite images which is already loaded into TImageList.
My code so far:
int imageindex = 123;
boost::scoped_ptr<TPngImage> png(new TPngImage);
boost::scoped_ptr<Graphics::TBitmap> bmp(new Graphics::TBitmap);
MyImageList->GetBitmap(imageindex, bmp.get()); // Using GetBitmap to copy TImageList image into separate TBitmap
png->Assign(bmp.get()); // Assign that bitmap to TPngImage
png->SaveToFile("C:\\filename.png");
The above works but it saves with the white background (transparency is not preserved after saving). I am probably missing a simple step but can't figure it out.
Delphi code is also welcome, shouldn't be hard to translate.
Yes, you can obtain PNG-image from TImageList where it was added. Code below allows you to do this!
Firstly, add PngImage to your uses clause.
procedure LoadPNGFromImageList(AImageList: TCustomImageList; AIndex: Integer; var ADestPNG: TPngImage);
const
PixelsQuad = MaxInt div SizeOf(TRGBQuad) - 1;
type
TRGBAArray = Array [0..PixelsQuad - 1] of TRGBQuad;
PRGBAArray = ^TRGBAArray;
var
ContentBmp: TBitmap;
RowInOut: PRGBAArray;
RowAlpha: PByteArray;
X: Integer;
Y: Integer;
begin
if not Assigned(AImageList) or (AIndex < 0) or
(AIndex > AImageList.Count - 1) or not Assigned(ADestPNG)
then
Exit;
ContentBmp := TBitmap.Create;
try
ContentBmp.SetSize(ADestPNG.Width, ADestPNG.Height);
ContentBmp.PixelFormat := pf32bit;
// Allocate zero alpha-channel
for Y:=0 to ContentBmp.Height - 1 do
begin
RowInOut := ContentBmp.ScanLine[Y];
for X:=0 to ContentBmp.Width - 1 do
RowInOut[X].rgbReserved := 0;
end;
ContentBmp.AlphaFormat := afDefined;
// Copy image
AImageList.Draw(ContentBmp.Canvas, 0, 0, AIndex, true);
// Now ContentBmp has premultiplied alpha value, but it will
// make bitmap too dark after converting it to PNG. Setting
// AlphaFormat property to afIgnored helps to unpremultiply
// alpha value of each pixel in bitmap.
ContentBmp.AlphaFormat := afIgnored;
// Copy graphical data and alpha-channel values
ADestPNG.Assign(ContentBmp);
ADestPNG.CreateAlpha;
for Y:=0 to ContentBmp.Height - 1 do
begin
RowInOut := ContentBmp.ScanLine[Y];
RowAlpha := ADestPNG.AlphaScanline[Y];
for X:=0 to ContentBmp.Width - 1 do
RowAlpha[X] := RowInOut[X].rgbReserved;
end;
finally
ContentBmp.Free;
end;
end;
Look at the picture. It is depicts what will happen if we set or not set such line of code:
ContentBmp.AlphaFormat := afIgnored;
Figure 1 is a result of setting afIgnored and the second one figure is a result of not setting afIgnored, allowing to use previously set afDefined.
Original image is an image named Figure 1
Using of code above in application:
procedure TForm1.aButton1Click(Sender: TObject);
var
DestPNG: TPngImage;
begin
DestPNG := TPNGImage.Create;
try
// Initialize PNG
DestPNG.CreateBlank(COLOR_RGBALPHA, 8, 60, 60);
// Obtain PNG from image list
LoadPNGFromImageList(ImageList1, 0, DestPNG);
// Output PNG onto Canvas
DestPNG.Draw(Canvas, Rect(0, 0, 60, 60));
DestPNG.SaveToFile('C:\MyPNGIcon.png');
finally
DestPNG.Free;
end;
end;

How to draw a translucent image on a form?

I want to a draw a translucent image on a Delphi form, but for some reason it is not working.
Here is the original PNG (border is semi transparent):
I load the image in a TImage object:
Image1.Transparent := True;
Form1.Color := clWhite;
Form1.TransparentColor := True;
Form1.TransparentColorValue := clWhite;
The application:
The image isn't translucent. I am working with a BMP image that contains the alpha channel. Am I missing something?
I found a solution that will let you draw a BMP image with an alpha channel onto a form using only the Windows API:
const
AC_SRC_OVER = 0;
AC_SRC_ALPHA = 1;
type
BLENDFUNCTION = packed record
BlendOp,
BlendFlags,
SourceConstantAlpha,
AlphaFormat: byte;
end;
function WinAlphaBlend(hdcDest: HDC; xoriginDest, yoriginDest, wDest, hDest: integer;
hdcSrc: HDC; xoriginSrc, yoriginSrc, wSrc, hSrc: integer; ftn: BLENDFUNCTION): LongBool;
stdcall; external 'Msimg32.dll' name 'AlphaBlend';
procedure TForm4.FormClick(Sender: TObject);
var
hbm: HBITMAP;
bm: BITMAP;
bf: BLENDFUNCTION;
dc: HDC;
begin
hbm := LoadImage(0,
'C:\Users\Andreas Rejbrand\Skrivbord\RatingCtrl.bmp',
IMAGE_BITMAP,
0,
0,
LR_LOADFROMFILE);
if hbm = 0 then
RaiseLastOSError;
try
if GetObject(hbm, sizeof(bm), #bm) = 0 then RaiseLastOSError;
dc := CreateCompatibleDC(0);
if dc = 0 then RaiseLastOSError;
try
if SelectObject(dc, hbm) = 0 then RaiseLastOSError;
bf.BlendOp := AC_SRC_OVER;
bf.BlendFlags := 0;
bf.SourceConstantAlpha := 255;
bf.AlphaFormat := AC_SRC_ALPHA;
if not WinAlphaBlend(Canvas.Handle,
10,
10,
bm.bmWidth,
bm.bmHeight,
dc,
0,
0,
bm.bmWidth,
bm.bmHeight,
bf) then RaiseLastOSError;
finally
DeleteDC(dc);
end;
finally
DeleteObject(hbm);
end;
end;
Using The GIMP, I converted the PNG image
found here to a 32-bit RGBA bitmap, found here, and the result is very good:
Why not try do draw your png onto new image with regular bmp. Draw what you want onto image 2 and redraw /or assign/ all to your image 1 when finish. Must works...
The TransparentColorValue approach cannot possibly work, because this only works with images in which a single colour represents full transparency. [In addition, you are toying with the form's transparent colour instead of image's transparent colour!] The above PNG image is supposed to have an alpha channel, so it's not like every pixel is either shown or transparent -- instead, each pixel has an opacity between 0 and 1 (0.37, for instance). That is, in addition to the R, G, and B components of each pixel, there is an 'alpha' component A.
The above image appears to be corrupt, however. A 'correct' PNG is shown below:
(source: rejbrand.se)
You can try to blend the above one onto different backgrounds, and you will find that the shadow blends nicely.
So, if one has a 'correct' PNG, how to draw it onto a form? Well, that is going to be very difficult in your case, since Delphi 7 does not support PNG images. It only supports BMP images, and these normally do not have alpha channels.

TBitmap drawing transparent image in Delphi 2009

Problem in drawing a semi transparent PNG image on TBitmap object.
If the TBitmap's ,HandleType is set to bmDDB, then the canvas is drawn transparent.
But the problem is it doesn't work on all kinds of machines (for ex: Windows on apple computers).
When a TBitmap's HandleType property is set to bmDIB, canvas background is drawn white.
bmp.HandleType := bmDIB;
I tried setting Brush style to bsClear. But it draws the transparent pixels in black color.
How can I draw an image preserving its transparency and smooth curved edges.
Thanks
Pavan.
It is certainly possible to paint a bmDIB bitmap with transparent background to a canvas:
procedure TForm1.FormPaint(Sender: TObject);
var
Bmp: TBitmap;
begin
Bmp := TBitmap.Create;
try
Bmp.PixelFormat := pf32bit;
Bmp.HandleType := bmDIB;
Bmp.Width := 700;
Bmp.Height := 400;
Bmp.Transparent := TRUE;
Bmp.TransparentColor := clMaroon;
with Bmp.Canvas do begin
Brush.Color := clMaroon;
FillRect(Rect(0, 0, Bmp.Width, Bmp.Height));
Brush.Color := clBlue;
FillRect(Rect(42, 42, 200, 300));
end;
Canvas.Draw(12, 12, Bmp);
finally
Bmp.Free;
end;
end;
Note that the whole bitmap is filled first with the colour set as TransparentColor.
But for more control and speed you should look into a solution that is not as dependent on the GDI (which involves graphics card and driver capabilities), something like Graphics32.

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