de.frame4j.graf

Interface ColorHelper

All Superinterfaces:

ColorVal

All Known Subinterfaces:

GrafHelper

@MinDoc(copyright="Copyright 2000 - 2009, 2016  A. Weinert",
        author="Albrecht Weinert",
        version="V.44",
        lastModified="6.05.2021",
        purpose="graphical helpers")
public interface ColorHelper
extends ColorVal

Colour helper methods.

This abstract class contains some helper methods; mainly:

• colour choice,

It is a subset of former GrafHelper
© Copyright 2000 - 2005, 2016 Albrecht Weinert

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	ColorHelper.Impl Private helper class.

Field Summary

Fields

Modifier and Type	Field and Description
static Action.Filter	colourChooseFilter A filter for Actions by code.
static ConcurrentHashMap<String,Color>	colourCmap HashMap for colours.
static CleverSSS	rkColIs The subsequence "color=" for white space and case ignoring search.

Fields inherited from interface de.frame4j.graf.ColorVal

bk, bl, COLOR_CHOOSE, dbl, dge, dgn, dgr, drt, dsi, dye, ge, gn, gr, hbl, hgr, hrd, hrt, nbl, or, pi, rd, rt, si, sw, ws, wt, ye

Method Summary

Modifier and Type	Method and Description
static Color	calcFgColor(Color bg) Determine a foreground colour for a given background colour.
static Color	getColor(CharSequence colourDef) Determine a colour by a character sequence.
static BufferedImage	scaleImage(Image img, Color bgColor, int newWidth, int newHeight) Scaling a picture.
static void	setBgColor(Component c, Color bg) Set a component's foreground and background colours.
static BufferedImage	surrondImage(Image img, Color bgColor, int upM, int loM, int leM, int riM) Surround a picture.

Field Detail

colourCmap

static final ConcurrentHashMap<String,Color> colourCmap

HashMap for colours.

Used to avoid multiple decoding and generating.
Filled / checked by getColor(CharSequence).

rkColIs

static final CleverSSS rkColIs

The subsequence "color=" for white space and case ignoring search.

colourChooseFilter

static final Action.Filter colourChooseFilter

A filter for Actions by code.

This filter accepts all s non null action with code "choose colour".

See Also:

Action, Action.SCOLOR

Method Detail

calcFgColor

static Color calcFgColor(Color bg)

Determine a foreground colour for a given background colour.

The colour returned to the given (background) colour bg is either white ColorVal.ws) or black (ColorVal.sw), depending on the (weighted) brightness of bg.
Algorithm: From bg's RGB values a gray value will be calculated, using ITU standard weights (222, 707, 71; according to recommendation 709, D65). About 51% will be used as threshold.

Parameters:

bg - the background colour (null returns black)

Returns:

a fitting / contrasting foreground either white or black

setBgColor

static void setBgColor(Component c,
                       Color bg)

Set a component's foreground and background colours.

The background colour of c will be set by bg.
The foreground colour will be set as white or black, whatever gives a good contrast to bg.

See Also:

calcFgColor(Color)

getColor

static Color getColor(CharSequence colourDef)

Determine a colour by a character sequence.

The character sequence colourDef is stripped from surrounding whitespace and quotes. If null or empty null is returned.

If the subsequence "color=" is found (ignoring white spaces) within colourDef only the token following the = is considered.

The sequence colourDef or its remaining token is interpreted decimal, octal or hexadecimal as 24 bit number to define a colour as RGB (0xrrggbb); see also Color.decode(String). A leading sharp (#) will be replaced before by 0x (#FFC0C0 -> 0xffcoco) to accept HTML colour values, too.

The second possible interpretation of colourDef is as an English, German or French colour name or industry standard abbreviation.

As an example, the following sequences (among others) will be understood as pure blue:

• 255
• "255"
• 0x0000ff
• blue
• blau
• bleu
• bl
• bcColor="blue" align="center"

See the hints at ColorVal.COLOR_CHOOSE.

If all (those toils of) interpretation fail, null is returned.

The lower cased token part of colourDef is used as key to a cache used and filled by this method. This partly avoids double decoding and generating.

Parameters:

colourDef - the colour definition

Returns:

Color fitting colourDef or null

See Also:

ColorVal.COLOR_CHOOSE, Action

surrondImage

static BufferedImage surrondImage(Image img,
                                  Color bgColor,
                                  int upM,
                                  int loM,
                                  int leM,
                                  int riM)

Surround a picture.

The given picture img ( 3 * 8 bit colour model) will be enlarged by the given margins (the result being returned as new image).

Is img null or of zero or unknown size, null will be returned.

If (just) one margin is outside the range 0 to 400, all (!) margins are set to 0.

Parameters:

img - the picture to be surrounded

bgColor - background respectively margin colour (default ColorVal.ws).

upM - upper margin in pixel (0..400).

loM - leM - riM - ditto lower, left and right.

Returns:

the picture as buffered image and (if given in range) surrounded / enlarged by margins

scaleImage

static BufferedImage scaleImage(Image img,
                                Color bgColor,
                                int newWidth,
                                int newHeight)

Scaling a picture.

The given picture img ( 3 * 8 bit colour model) will be stretched or shrunk to the given size and returned as BufferedImage.

Is img null or of zero or unknown size, null or is the one of the wanted sizes less than 1, null will be returned.

Are the given and ordered dimensions the same and is img of type BufferedImage, img itself will be returned (not copied).

Parameters:

img - the picture to scale

bgColor - background colour (used to prefill the new buffered image, if not null)

newHeight - new height

newWidth - new width

Returns:

the scaled picture as buffered image