Here’s the code.<\/p>\n
This is particularly neat to use if you want to place text on a bitmap and
\nguarantee that the text is readable without completely obscuring the image
\nunderneath; simply tint the area underneath the text with clBlack, then draw
\nclWhite text on top (with Canvas.Brush.Style = bsClear).<\/p>\n
Note that the TintBitmapRect procedure below requires that you’re using
\npf32Bit bitmaps. It can be modified to work with other pixel formats, but
\nthat is an exercise for the reader.
\n
\n[code lang=”delphi”]{
\n TColors have color components in blue-green-red order.
\n 32-bit bitmap pixels have color components in red-green-blue order.
\n This function allows conversion between the two orders.
\n}
\nfunction SwapRedBlue(const Color: TColor): TColor;<\/p>\n
begin
\n Result := (Color and $FF0000) shr 16 or
\n (Color and $00FF00) or
\n (Color and $0000FF) shl 16;
\nend;<\/p>\n
{
\n Tint an arbitrary rectangular area of a bitmap with an arbitrary color.<\/p>\n
Author: Gary Williams, gw (at) gw (dot) ro
\n}
\nprocedure TintBitmapRect(const Bitmap: TBitmap;
\n const Rect: TRect;
\n const Color: TColor);<\/p>\n
var
\n Pixel: PLongWord;<\/p>\n
I: Integer;
\n J: Integer;<\/p>\n
Color2: LongWord;<\/p>\n
const
\n Mask: LongWord = $00FEFEFE;<\/p>\n
begin
\n Assert(Bitmap.PixelFormat = pf32Bit);<\/p>\n
Color2 := SwapRedBlue(Color) and Mask;<\/p>\n
for I := Rect.Top to (Rect.Bottom – 1) do
\n begin
\n Pixel := Bitmap.ScanLine[I];
\n Inc(Pixel, Rect.Left);<\/p>\n
for J := Rect.Left to (Rect.Right – 1) do
\n begin
\n Pixel^ := ((Pixel^ and Mask) + Color2) shr 1;
\n Inc(Pixel);
\n end;
\n end;
\nend;<\/p>\n
procedure TForm1.Button1Click(Sender: TObject);<\/p>\n
begin
\n with Image1.Picture do
\n begin
\n Bitmap.PixelFormat := pf32Bit;<\/p>\n
TintBitmapRect(Bitmap,
\n Rect(Bitmap.Width div 4,
\n Bitmap.Height div 4,
\n Bitmap.Width – Bitmap.Width div 4,
\n Bitmap.Height – Bitmap.Height div 4),
\n clRed);
\n end;
\nend;
\n[\/code]<\/p>\n
[tags]Delphi, Graphic[\/tags]<\/p>\n","protected":false},"excerpt":{"rendered":"
Here’s the code. This is particularly neat to use if you want to place text on a bitmap and guarantee that the text…<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[11],"tags":[75,101],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p71Tml-2v","_links":{"self":[{"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/posts\/155"}],"collection":[{"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/comments?post=155"}],"version-history":[{"count":0,"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/posts\/155\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/media?parent=155"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/categories?post=155"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.nsonic.de\/blog\/wp-json\/wp\/v2\/tags?post=155"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}