Revision 1 of 2, by Circular on 5-4-2015. The page as it is now.

TBGRACustomBitmap and IBGRAScanner

Back to BGRABitmap.

This class and this interface are included in BGRABitmapTypes.

For methods (procedure and functions), see TBGRABitmap class.

TBGRACustomBitmap and IBGRAScanner

IBGRAScanner

IBGRAScanner = interface

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Interface for a scanner. A scanner is like an image, but its content has no limit and it can be calculated on the fly. It is like a infinite readonly image.

Note: it must not implement reference counting even if it is an interface

TBGRACustomBitmap implements this interface and the content is repeated horizontally and vertically. There are also various classes in BGRAGradientScanner unit that generate gradients on the fly and in BGRATransform unit that provide geometrical transformations of images

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procedure ScanMoveTo(X,Y: Integer);

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Move to the position (X,Y) for the next call to ScanNextPixel

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function ScanNextPixel: TBGRAPixel;

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Scan the pixel at the current location and increments X

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function ScanAt(X,Y: Single): TBGRAPixel;

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Scan at any location using floating point coordinates

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function ScanAtInteger(X,Y: integer): TBGRAPixel;

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Scan at any location using integer coordinates

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procedure ScanPutPixels(pdest: PBGRAPixel; count: integer; mode: TDrawMode);

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Copy a row of pixels from X to X+count-1 to a specified destination pdest. mode indicates how to combine with existing data

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function IsScanPutPixelsDefined: boolean;

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Returns True if the function ScanPutPixels is available. Otherwise you need to call ScanNextPixel and combine pixels for example with SetPixel

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TScanAtFunction = function (X,Y: Single): TBGRAPixel of object;

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A type of function of a scanner that returns the content at floating point coordinates

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TScanAtIntegerFunction = function (X,Y: Integer): TBGRAPixel of object;

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A type of function of a scanner that returns the content at integer coordinates

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TScanNextPixelFunction = function: TBGRAPixel of object;

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A type of function of a scanner that returns the next pixel

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TBGRACustomScanner = class(IBGRAScanner)

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Base class for implementing IBGRAScanner interface

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TBGRACustomBitmap

TBGRACustomBitmap = class(TFPCustomImage,IBGRAScanner)

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This is the base class for TBGRABitmap. It is the direct parent of TBGRADefaultBitmap class, which is the parent of the diverse implementations. A bitmap can be used as a scanner using the interface IBGRAScanner

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Caption: string;

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User defined caption. It does not appear on the image

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FillMode: TFillMode;

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Method to use when filling polygons (winding or alternate). See BGRAGraphics

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LinearAntialiasing: boolean;

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Specifies if linear antialiasing must be used when drawing antialiased shapes

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ResampleFilter : TResampleFilter;

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Resample filter is used when resizing the bitmap. See resampling types

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ScanInterpolationFilter: TResampleFilter;

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Scan interpolation filter is used when the bitmap is used as a scanner (interface IBGRAScanner)

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ScanOffset: TPoint;

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Offset to apply when the image is scanned using IBGRAScanner interface

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property Width: integer read;

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Width of the image in pixels

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property Height: integer read;

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Height of the image in pixels

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property ClipRect: TRect read write;

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Clipping rectangle for all drawing functions

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property NbPixels: integer read;

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Total number of pixels. It is always true that NbPixels = Width * Height

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property ScanLine[y: integer]: PBGRAPixel read;

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Returns the address of the left-most pixel of any line. The parameter y ranges from 0 to Height-1

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property LineOrder: TRawImageLineOrder read;

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Indicates the order in which lines are stored in memory. If it is equal to riloTopToBottom, the first line is the top line. If it is equal to riloBottomToTop, the first line is the bottom line. See miscellaneous types

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property Data: PBGRAPixel read;

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Provides a pointer to the first pixel in memory. Depending on the LineOrder property, this can be the top-left pixel or the bottom-left pixel. There is no padding between scanlines, so the start of the next line is at the address Data + Width. See BGRABitmap tutorial 4

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property RefCount: integer read;

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Number of references to this image. It is increased by the function NewReference and decreased by the function FreeReference

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property Empty: boolean read;

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Returns True if the bitmap only contains transparent pixels or has a size of zero

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property HasTransparentPixels: boolean read;

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Returns True if there are transparent or semitransparent pixels, and so if the image would be stored with an alpha channel

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property AverageColor: TColor read;

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Average color of the image

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property AveragePixel: TBGRAPixel read;

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Average color (including alpha) of the image

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property CanvasFP: TFPImageCanvas read;

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Canvas compatible with FreePascal

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property CanvasDrawModeFP: TDrawMode read write;

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Draw mode to used when image is access using FreePascal functions and Colors property

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property Bitmap: TBitmap read;

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Bitmap in a format compatible with the current GUI. Don't forget to call InvalidateBitmap before using it if you changed something with direct pixel access (Scanline and Data)

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property Canvas: TCanvas read;

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Canvas provided by the GUI

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property CanvasOpacity: byte read write;

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Opacity to apply to changes made using GUI functions, provided CanvasAlphaCorrection is set to True

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property CanvasAlphaCorrection: boolean read write;

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Specifies if the alpha values must be corrected after GUI access to the bitmap

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JoinStyle: TPenJoinStyle;

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How to join segments. See BGRAGraphics

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JoinMiterLimit: single;

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Limit for the extension of the segments when joining them with pjsMiter join style, expressed in multiples of the width of the pen

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property PenStyle: TPenStyle read write;

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Pen style. See BGRAGraphics

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property CustomPenStyle: TBGRAPenStyle read write;

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Custom pen style. See geometric types

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property LineCap: TPenEndCap read write;

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How to draw the ends of a line

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property ArrowStartSize: TPointF read write;

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Size of arrows at the start of the line

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property ArrowEndSize: TPointF read write;

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Size of arrows at the end of the line

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property ArrowStartOffset: single read write;

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Offset of the arrow from the start of the line

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property ArrowEndOffset: single read write;

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Offset of the arrow from the end of the line

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property ArrowStartRepeat: integer read write;

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Number of times to repeat the starting arrow

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property ArrowEndRepeat: integer read write;

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Number of times to repeat the ending arrow

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FontName: string;

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Specifies the font to use. Unless the font renderer accept otherwise, the name is in human readable form, like 'Arial', 'Times New Roman', ...

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FontStyle: TFontStyles;

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Specifies the set of styles to be applied to the font. These can be fsBold, fsItalic, fsStrikeOut, fsUnderline. So the value [fsBold,fsItalic] means that the font must be bold and italic. See miscellaneous types

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FontQuality : TBGRAFontQuality;

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Specifies the quality of rendering. Default value is fqSystem. See miscellaneous types

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FontOrientation: integer;

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Specifies the rotation of the text, for functions that support text rotation. It is expressed in tenth of degrees, positive values going counter-clockwise.

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FontVerticalAnchor: TFontVerticalAnchor;

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Specifies how the font is vertically aligned relative to the start coordinate. See miscellaneous types

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property FontHeight: integer read write;

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Specifies the height of the font in pixels without taking into account additional line spacing. A negative value means that it is the full height instead (see below)

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property FontFullHeight: integer read write;

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Specifies the height of the font in pixels, taking into account the additional line spacing defined for the font

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property FontAntialias: Boolean read write;

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Simplified property to specify the quality (see FontQuality)

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property FontPixelMetric: TFontPixelMetric read;

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Returns measurement for the current font in pixels

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property FontRenderer: TBGRACustomFontRenderer read write;

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Specifies the font renderer. When working with the LCL, by default it is an instance of TLCLFontRenderer of unit BGRAText. Other renderers are provided in BGRATextFX unit and BGRAVectorize unit. Additionally, BGRAFreeType provides a renderer independent from the LCL.

Once you assign a renderer, it will automatically be freed when the bitmap is freed. The renderers may provide additional styling for the font, not accessible with the properties in this class

See font rendering

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Load and save files

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procedure LoadFromFile(const filename: string); virtual;

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Load image from a file. filename is an ANSI string

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procedure LoadFromFile(const filename:string; Handler:TFPCustomImageReader); virtual;

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Load image from a file with the specified image reader. filename is an ANSI string

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procedure LoadFromFileUTF8(const filenameUTF8: string); virtual;

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Load image from a file. filename is an UTF8 string

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procedure LoadFromFileUTF8(const filenameUTF8: string; AHandler: TFPCustomImageReader); virtual;

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Load image from a file with the specified image reader. filename is an UTF8 string

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procedure LoadFromStream(Str: TStream); virtual; overload;

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Load image from a stream. Format is detected automatically

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procedure LoadFromStream(Str: TStream; Handler: TFPCustomImageReader); virtual; overload;

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Load image from a stream. The specified image reader is used

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procedure SaveToFile(const filename: string); virtual; overload;

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Save image to a file. The format is guessed from the file extension. filename is an ANSI string

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procedure SaveToFile(const filename: string; Handler:TFPCustomImageWriter); virtual; overload;

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Save image to a file with the specified image writer. filename is an ANSI string

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procedure SaveToFileUTF8(const filenameUTF8: string); virtual; overload;

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Save image to a file. The format is guessed from the file extension. filename is an ANSI string

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procedure SaveToFileUTF8(const filenameUTF8: string; Handler:TFPCustomImageWriter); virtual; overload;

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Save image to a file with the specified image writer. filename is an UTF8 string

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procedure SaveToStream (Str:TStream; Handler:TFPCustomImageWriter);

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Save image to a stream with the specified image writer

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procedure SaveToStreamAs(Str: TStream; AFormat: TBGRAImageFormat); virtual;

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Save image to a stream in the specified image format

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procedure SaveToStreamAsPng(Str: TStream); virtual;

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Save image to a stream in PNG format

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procedure LoadFromDevice(DC: System.THandle); virtual; abstract; overload;

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Gets the content of the specified device context

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procedure LoadFromDevice(DC: System.THandle; ARect: TRect); virtual; abstract; overload;

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Gets the content from the specified rectangular area of a device context

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procedure TakeScreenshotOfPrimaryMonitor; virtual; abstract;

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Fills the content with a screenshot of the primary monitor

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procedure TakeScreenshot(ARect: TRect); virtual; abstract;

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Fills the content with a screenshot of the specified rectangular area of the desktop (it can be from any screen)

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For more methods, see derived class TBGRABitmap

From the Free Pascal wiki, page "TBGRACustomBitmap and IBGRAScanner", as it stood on 2015-05-04 after a change by Circular, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.