ImageEn, unit imageenproc




procedure ConvertTo(NumColors: Integer; DitherMethod: TIEDitherMethod = ieOrdered);
function ConvertTo(PixelFormat: TIEPixelFormat; PaletteType: TIEPaletteType = ieptMedianCut; DitherType: TIEDitherType = iedtSolid; CheckParametersOnly: boolean = false): boolean;
function ConvertTo(PixelFormat: TIEPixelFormat; Palette: array of TRGB; DitherType: TIEDitherType = iedtSolid; CheckParametersOnly: boolean = false): boolean; overload;


First overload reduces the number of colors in the image.

Parameter Description
NumColors Number of colors of the resulting image
DitherMethod Color conversion algorithm to use
Palette Specify a custom palette (up to 256 color entries)

When ieDithering is used and the required number of colors is <= 256 the resulting pixel format will be ie8p (unless LegacyBitmap is true or Location is ieTBitmap).

Second overload changes image pixel format using a combination of palette type and dithering algorithm when necessary.
This method may disable LegacyBitmap property if necessary.
Not all combinations of parameters are possible, check the return value. Returns True on success.

Third overload forces use of a specified palette.

Parameter Description
PixelFormat Required pixel format. Can be: ie1g, ie8p, ie8g, ie16g, ie24RGB, ieCMYK, ie48RGB
PaletteType Palette type to use when reducing colors (Do not use ieptFixedBW if you are using an ordered dithering, such as iedtOrdered8x8)
DitherType Dither type to use when reducing colors (If NumColors is <= 2 then only ieOrdered and ieThreshold are supported. If NumColors is > 2 then only ieDithering and ieOrdered are supported, If NumColors is > 256, then only ieOrdered is supported)
CheckParametersOnly If True, does not actually convert the image, just checks parameters validity

 If a palette is required, use ConvertToPalette
 Any selection is ignored. The whole image is converted to the specified palette
 A quantizer is used to reduce the number of colors using the method specified by ColorReductionAlgorithm


Demo  Demos\ImageEditing\Dithering\Dithering.dpr
Demo  Demos\InputOutput\BatchConvert\BatchConvert.dpr
Demo  Demos\ImageEditing\EveryMethod\EveryMethod.dpr

Method Testing

ImageEnView1.IO.LoadFromFile( 'D:\TestImage.jpg' );


// Convert to a 4-color ordered palette
ImageEnView1.Proc.ConvertTo( 4, ieOrdered );


// Convert to a 4-color dithered palette
ImageEnView1.Proc.ConvertTo( 4, ieDithering );


// Convert to a 16-color ordered palette
ImageEnView1.Proc.ConvertTo( 16, ieOrdered );


// Convert to a 16-color dithered palette
ImageEnView1.Proc.ConvertTo( 16, ieDithering );


// Convert to a 64-color ordered palette
ImageEnView1.Proc.ConvertTo( 64, ieOrdered );


// Convert to a 64-color dithered palette
ImageEnView1.Proc.ConvertTo( 64, ieDithering );



// Convert current image to 256 colors

// Convert current image to 461 (!) colors

// Convert current image to 16 colors, using Floyd-Steinberg dithering
ImageEnView1.Proc.ConvertTo(16, ieDithering);

// Convert pixel format to 256 colors with palette, using halftone palette and 8x8 dithering
ImageEnView1.Proc.ConvertTo(ie8p, ieptFixedHalftone256, iedtOrdered8x8);

// Convert pixel format to monochrome using halftone palette and 8x8 dithering
imageenview1.Proc.ConvertTo(ie1g, ieptFixedHalftone256, iedtOrdered8x8);

// Convert pixel format to monochrome with solid dithering
ImageEnView1.proc.ConvertTo(ie1g, ieptFixedBW, iedtSolid);

// Load a full-color image and save it as 256 color one
ImageEnView1.Proc.ConvertTo(ie8p, ieptFixedHalftone256, iedtOrdered8x8);
ImageEnView1.IO.Params.BitsPerSample := 8;
ImageEnView1.IO.Params.SamplesPerPixel := 1;

// Convert to 8 bits per pixel using the specified palette
const MYPALETTE: array [0..7] of TRGB = ((B: 0; G: 0; R:0), (B: 51; G: 0; R:0), (B: 102; G: 0; R:0), (B: 153; G: 0; R:0), (B: 204; G: 0; R:0), (B: 255; G: 0; R:0), (B: 0; G: 51; R:0), (B: 51; G: 51; R:0));
ImageEnView1.Proc.ConvertTo(ie8p, MYPALETTE, iedtErrorDiffusion);
ImageEnView1.IO.Params.BitsPerSample := 8;
ImageEnView1.IO.Params.SamplesPerPixel := 1;

// Reduce image to colors within 216 color web palette (6 level RGB)
  Color_Steps: array[0..5] of byte = (0,51,102,153,204,255);
  Palette: array[0..215] OF TRGB;
  I: Cardinal;
  R,G,B: BYTE;
  I := LOW(Palette);
  For R := 0 to 5 do
    For G := 0 to 5 do
      For B := 0 to 5 do
        Palette[ i ] := CreateRGB( Color_Steps[R], Color_Steps[G], Color_Steps[B]);
  ImageEnView1.Proc.ConvertTo(ie8p, Palette, iedtErrorDiffusion);

See Also