TIEBitmap.RenderToCanvas

Declaration

procedure RenderToCanvas(DestCanvas: TCanvas; xDst, yDst, dxDst, dyDst: integer; Filter: TResampleFilter; Gamma: double = 0; BackgroundColor: TColor = clWhite; MaintainAR: Boolean = False); overload;
procedure RenderToCanvas(DestCanvas: TCanvas; DestRect: TRect; Filter: TResampleFilter; Gamma: double = 0; BackgroundColor: TColor = clWhite; MaintainAR: Boolean = False); overload;

Description

Draws the bitmap to the DestCanvas at the rectangle specified by xDst, yDst, dxDst, dyDst.
Filter specifies the filter if the image needs to be resampled.
Gamma is the gamma correction.
BackgroundColor specifies the background color when pixels aren't opaque.
MaintainAR adjusts the passed destination values to ensure the image is not skewed (maintains its original aspect ratio).

Note: If RenderToCanvas is used with an image with an alpha channel, the image will be modified. Use RenderToCanvasWithAlpha if the source bitmap has an alpha channel that should be respected when drawing.

Example

// Col 1 of a TStringGrid displays a thumbnail drawn from a TImageEnMView
procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Longint;
  Rect: TRect; State: TGridDrawState);
var
  aIEBitmap: IEBitmap;
  aCanvas: TCanvas;
  idx: Integer;
begin
  // Col 1 contains thumbnail. Row 0 is fixed header row
  if (ACol <> 1) or (ARow = 0) then
    Exit;

  idx := ARow;
  aCanvas := (Sender as TStringGrid).Canvas;

  // Clear current cell rect
  aCanvas.FillRect( Rect );

  // Get our image
  // Note: don't need to create or free the TIEBitmap
  aIEBitmap := ImageEnMView1.GetIEBitmap( idx );

  // Adjust our rect to maintain the image aspect ratio
  Rect := GetImageRectWithinArea( Rect, aIEBitmap.Width, aIEBitmap.Height );

  // Draw the image
  aIEBitmap := RenderToCanvas( aCanvas, Rect.Left, Rect.Top, Rect.Right - Rect.Left,   Rect.Bottom - Rect.Top, rfFastLinear, 0 );

  // Release our image
  ImageEnMView1.ReleaseBitmap( idx, False );
end;

TIEBitmap Assignment and Drawing Methods

TIEBitmap Methods

Method	Mode	Purpose
Assign	From TIEBitmap/TBitmap/TGraphic/TIcon	Copy whole image
AssignImage	From TIEBitmap	Like assign, but does not copy the alpha channel
AssignRect	From TIEBitmap/TBitmap	Copy a specified rect
CopyAndConvertFormat	From TIEBitmap	Copy whole image
CopyRectTo	To TIEBitmap	Copy rect to another image (without scaling)
CopyWithMask1	To TIEBitmap	Copy image using a mask to specify what is copied from the source
CopyWithMask2	To TIEBitmap	Copy image using a mask to specify what is replaced in the destintation
DrawToTIEBitmap	To TIEBitmap	Copies all or part of the image to a specified position and/or size
JoinBitmaps	From two TIEBitmaps	Draws two bitmaps to a single bitmap
MergeAlphaRectTo	With TIEBitmap	Merges the alpha channels of two TIEBitmaps using merge rules
MergeWithAlpha	With TIEBitmap	Merges all or part of two TIEBitmaps with alpha channels to a specified position
RenderToTIEBitmapEx	To TIEBitmap	Extended drawing of content to a TIEBitmap
StretchRectTo	To TIEBitmap	Copy rect to dest rect in another image (with scaling)
SwitchTo	To TIEBitmap	Move content from one TIEBitmap to another

TBitmap Methods

Method	Mode	Purpose
Assign	From TIEBitmap/TBitmap/TGraphic/TIcon	Copy whole image
AssignTo	To TIEBitmap/TBitmap	Copy whole image with optional scaling
AssignRect	From TIEBitmap/TBitmap	Copy a specified rect
CopyFromTBitmap	From TBitmap	Copy whole image
CopyToTBitmap	To TBitmap	Copy whole image
RenderToTBitmapEx	To TBitmap	Extended drawing of content to a TBitmap

TCanvas Methods

Method	Mode	Purpose
DrawToCanvas	To TCanvas	Copies whole image to canvas at specified position (ignoring the alpha channel)
DrawToCanvasWithAlpha	To TCanvas	Copies whole image to canvas at specified position (honoring the alpha channel)
RenderToCanvas	To TCanvas	Extended drawing of content to a TCanvas (ignoring the alpha channel)
RenderToCanvasWithAlpha	To TCanvas	Extended drawing of content to a TCanvas (honoring the alpha channel)

TIEBitmap.RenderToCanvas