Mega Code Archive
Textantialias
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If you want to have anti-aliased text independant of the API, you can look
into the Graphics32 library at http://www.geocities.com/den_alex. It
supports 32-bit bitmaps with alpha blending and also offers varying levels
of anti-aliasing on text and lines.
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Liviu Uba wrote:
> When you draw a Text on Canvas using DrawText API or simply Canvas
> methods like TextRect(whichis mainly the same), the font is ANTI-ALIASED
> with the brush color and it looks fine...
> How can one implement this nice drawing on a BITMAP, since the Brush
> cannot be invisible..
Here are a group of related functions (which I built up from a variety of
sources) that I use to render font characters as anti-aliased bitmaps - I
hope it helps:
// Draw the font character as a bitmap, setting the size, background and
// foreground colours, colour depth and whether or not to anti-alias the
// image.
// Based on code by Earl F. Glynn and Mike Lischke
procedure TfrmTT2Img.CharacterToGraphic(Ht, Wd: cardinal;
FontName, ChrStr: string;
FontColor, BGColor: TColor;
ColDepth: TPixelFormat; AntiAlias:
boolean);
var
bmp: TBitmap;
Rect: TRect;
out_bmp,big_bmp: TBitmap;
begin
//Draw the font character as a bitmap image...
bmp := TBitmap.Create;
try
with bmp do
begin
Width := Wd;
Height := Ht;
PixelFormat := ColDepth;
with Canvas do
begin
Brush.Color := BGColor;
FillRect(bmp.Canvas.ClipRect);
Font.Name := FontName;
Font.Height := bmp.Height;
Font.Color := FontColor;
end;
Rect := Canvas.ClipRect;
ExtTextOutW(Canvas.Handle,0,0,ETO_CLIPPED,@Rect,pWideChar(ChrStr),Length(Chr
Str), NIL);
end;
CenterText(bmp.Canvas, Rect, ChrStr);
if AntiAlias then
begin
// To get accurate, antialiased rendering of the image,
// draw it scaled at an enlarged size...
big_bmp := TBitmap.Create;
try
SampleBitmap(Ht,Wd,FontName,ChrStr,FontColor,BGColor,big_bmp);
// ...now reduce it to the desired output size, recalculating
the
// output pixel color. The output color is obtained as an
average
// of the red, green and blue values of each of the 9 pixels in
// the enlarged image that correspond to a single pixel in the
//output image
out_bmp := TBitmap.Create;
try
with out_bmp do
begin
Width := bmp.Width;
Height := bmp.Height;
PixelFormat := pf24bit;
end;
AntiAliasPicture(bmp,big_bmp,out_bmp);
imgChar.Picture.Graphic := out_bmp;
finally
out_bmp.Free;
end;
finally
big_bmp.Free;
end;
end
else
begin
imgChar.Picture.Graphic := bmp;
end;
finally
bmp.Free
end;
end;
procedure SampleBitmap(Ht,Wd: cardinal; FontName, ChrStr: string;
FontColor, BGColor: TColor; var big_bmp:
TBitmap);
var
Rect: TRect;
begin
with big_bmp do
begin
Width := Wd*3;
Height := Ht*3;
PixelFormat := pf24Bit;
with Canvas do
begin
Brush.Color := BGColor;
FillRect(big_bmp.Canvas.ClipRect);
Font.Name := FontName;
Font.Height := big_bmp.Height;
Font.Color := FontColor;
end;
Rect := Canvas.ClipRect;
ExtTextOutW(Canvas.Handle,0,0,ETO_CLIPPED,@Rect,pWideChar(ChrStr),Length(Chr
Str), NIL);
end;
CenterText(big_bmp.Canvas, Rect, ChrStr);
end;
//Code by Earl F. Glynn
procedure CenterText(const Canvas: TCanvas; const Rect: TRect; const s:
string);
var
X,Y: integer;
begin
X := (Rect.Left + Rect.Right - Canvas.TextWidth(s)) div 2;
Y := (Rect.Top + Rect.Bottom - Canvas.TextHeight(s)) div 2;
Canvas.TextRect(Rect,X,Y,s);
end;
//From code by Nacho Urenda
procedure AntiAliasPicture(orig_bmp, big_bmp: TBitmap; var out_bmp:
TBitmap);
const
MaxPixelCount = 32768;
type
pRGBArray = ^TRGBArray;
TRGBArray = array[0..MaxPixelCount-1] of TRGBTriple;
var
x, y, cx, cy : integer;
totr, totg, totb : integer;
Row1, Row2, Row3, DestRow: pRGBArray;
i: integer;
begin
// For each row
for y := 0 to orig_bmp.Height - 1 do
begin
// We compute samples of 3 x 3 pixels
cy := y*3;
// Get pointers to actual, previous and next rows in supersampled bitmap
Row1 := big_bmp.ScanLine[cy];
Row2 := big_bmp.ScanLine[cy+1];
Row3 := big_bmp.ScanLine[cy+2];
// Get a pointer to destination row in output bitmap
DestRow := out_bmp.ScanLine[y];
// For each column...
for x := 0 to orig_bmp.Width - 1 do
begin
// We compute samples of 3 x 3 pixels
cx := 3*x;
// Initialize result color
totr := 0;
totg := 0;
totb := 0;
// For each pixel in sample
for i := 0 to 2 do
begin
// New red value
totr := totr + Row1[cx + i].rgbtRed
+ Row2[cx + i].rgbtRed
+ Row3[cx + i].rgbtRed;
// New green value
totg := totg + Row1[cx + i].rgbtGreen
+ Row2[cx + i].rgbtGreen
+ Row3[cx + i].rgbtGreen;
// New blue value
totb := totb + Row1[cx + i].rgbtBlue
+ Row2[cx + i].rgbtBlue
+ Row3[cx + i].rgbtBlue;
end;
// Set output pixel colors
DestRow[x].rgbtRed := totr div 9;
DestRow[x].rgbtGreen := totg div 9;
DestRow[x].rgbtBlue := totb div 9;
end;
end;
end;
Mike Gibbard
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