java.lang.Object java.awt.RenderingHints
public class RenderingHints
The RenderingHints class defines and manages collections of keys and associated values which allow an application to provide input into the choice of algorithms used by other classes which perform rendering and image manipulation services. The
Graphics2D
The RenderingHints class contains rendering hints that can be used by the
Graphics2D
class, and classes that implement
BufferedImageOp
and
RasterOp
Raster
all provide methods to get and possibly to set individual or groups of RenderingHints keys and their associated values. When those implementations perform any rendering or image manipulation operations they should examine the values of any RenderingHints that were requested by the caller and tailor the algorithms used accordingly and to the best of their ability.
.
Note that since these keys and values are hints , there is no requirement that a given implementation supports all possible choices indicated below or that it can respond to requests to modify its choice of algorithm. The values of the various hint keys may also interact such that while all variants of a given key are supported in one situation, the implementation may be more restricted when the values associated with other keys are modified. For example, some implementations may be able to provide several types of dithering when the antialiasing hint is turned off, but have little control over dithering when antialiasing is on. The full set of supported keys and hints may also vary by destination since runtimes may use different underlying modules to render to the screen, or to BufferedImage objects, or while printing.
Implementations are free to ignore the hints completely, but should try to use an implementation algorithm that is as close as possible to the request. If an implementation supports a given algorithm when any value is used for an associated hint key, then minimally it must do so when the value for that key is the exact value that specifies the algorithm.
The keys used to control the hints are all special values that subclass the associated RenderingHints.Key class. Many common hints are expressed below as static constants in this class, but the list is not meant to be exhaustive. Other hints may be created by other packages by defining new objects which subclass the Key class and defining the associated values.
Nested Class Summary | |
---|---|
static class |
RenderingHints.Key
Defines the base type of all keys used along with |
Nested classes/interfaces inherited from interface java.util. Map |
---|
Map.Entry < K , V > |
Field Summary | |
---|---|
static RenderingHints.Key |
KEY_ALPHA_INTERPOLATION
Alpha interpolation hint key. |
static RenderingHints.Key |
KEY_ANTIALIASING
Antialiasing hint key. |
static RenderingHints.Key |
KEY_COLOR_RENDERING
Color rendering hint key. |
static RenderingHints.Key |
KEY_DITHERING
Dithering hint key. |
static RenderingHints.Key |
KEY_FRACTIONALMETRICS
Font fractional metrics hint key. |
static RenderingHints.Key |
KEY_INTERPOLATION
Interpolation hint key. |
static RenderingHints.Key |
KEY_RENDERING
Rendering hint key. |
static RenderingHints.Key |
KEY_STROKE_CONTROL
Stroke normalization control hint key. |
static RenderingHints.Key |
KEY_TEXT_ANTIALIASING
Text antialiasing hint key. |
static RenderingHints.Key |
KEY_TEXT_LCD_CONTRAST
LCD text contrast rendering hint key. |
static Object |
VALUE_ALPHA_INTERPOLATION_DEFAULT
Alpha interpolation hint value -- alpha blending algorithms are chosen by the implementation for a good tradeoff of performance vs. |
static Object |
VALUE_ALPHA_INTERPOLATION_QUALITY
Alpha interpolation hint value -- alpha blending algorithms are chosen with a preference for precision and visual quality. |
static Object |
VALUE_ALPHA_INTERPOLATION_SPEED
Alpha interpolation hint value -- alpha blending algorithms are chosen with a preference for calculation speed. |
static Object |
VALUE_ANTIALIAS_DEFAULT
Antialiasing hint value |
static Object |
VALUE_ANTIALIAS_OFF
Antialiasing hint value |
static Object |
VALUE_ANTIALIAS_ON
Antialiasing hint value |
static Object |
VALUE_COLOR_RENDER_DEFAULT
Color rendering hint value -- perform color conversion calculations as chosen by the implementation to represent the best available tradeoff between performance and accuracy. |
static Object |
VALUE_COLOR_RENDER_QUALITY
Color rendering hint value -- perform the color conversion calculations with the highest accuracy and visual quality. |
static Object |
VALUE_COLOR_RENDER_SPEED
Color rendering hint value -- perform the fastest color conversion to the format of the output device. |
static Object |
VALUE_DITHER_DEFAULT
Dithering hint value |
static Object |
VALUE_DITHER_DISABLE
Dithering hint value |
static Object |
VALUE_DITHER_ENABLE
Dithering hint value |
static Object |
VALUE_FRACTIONALMETRICS_DEFAULT
Font fractional metrics hint value |
static Object |
VALUE_FRACTIONALMETRICS_OFF
Font fractional metrics hint value |
static Object |
VALUE_FRACTIONALMETRICS_ON
Font fractional metrics hint value |
static Object |
VALUE_INTERPOLATION_BICUBIC
Interpolation hint value -- the color samples of 9 nearby integer coordinate samples in the image are interpolated using a cubic function in both X and Y to produce a color sample. |
static Object |
VALUE_INTERPOLATION_BILINEAR
Interpolation hint value -- the color samples of the 4 nearest neighboring integer coordinate samples in the image are interpolated linearly to produce a color sample. |
static Object |
VALUE_INTERPOLATION_NEAREST_NEIGHBOR
Interpolation hint value -- the color sample of the nearest neighboring integer coordinate sample in the image is used. |
static Object |
VALUE_RENDER_DEFAULT
Rendering hint value |
static Object |
VALUE_RENDER_QUALITY
Rendering hint value |
static Object |
VALUE_RENDER_SPEED
Rendering hint value |
static Object |
VALUE_STROKE_DEFAULT
Stroke normalization control hint value -- geometry may be modified or left pure depending on the tradeoffs in a given implementation. |
static Object |
VALUE_STROKE_NORMALIZE
Stroke normalization control hint value -- geometry should be normalized to improve uniformity or spacing of lines and overall aesthetics. |
static Object |
VALUE_STROKE_PURE
Stroke normalization control hint value -- geometry should be left unmodified and rendered with sub-pixel accuracy. |
static Object |
VALUE_TEXT_ANTIALIAS_DEFAULT
Text antialiasing hint value -- text rendering is done according to |
static Object |
VALUE_TEXT_ANTIALIAS_GASP
Text antialiasing hint value -- text rendering is requested to use information in the font resource which specifies for each point size whether to apply VALUE_TEXT_ANTIALIAS_ON |
static Object |
VALUE_TEXT_ANTIALIAS_LCD_HBGR
Text antialiasing hint value -- request that text be displayed optimised for an LCD display with subpixels in order from display left to right of B,G,R such that the horizontal subpixel resolution is three times that of the full pixel horizontal resolution (HBGR). |
static Object |
VALUE_TEXT_ANTIALIAS_LCD_HRGB
Text antialiasing hint value -- request that text be displayed optimised for an LCD display with subpixels in order from display left to right of R,G,B such that the horizontal subpixel resolution is three times that of the full pixel horizontal resolution (HRGB). |
static Object |
VALUE_TEXT_ANTIALIAS_LCD_VBGR
Text antialiasing hint value -- request that text be displayed optimised for an LCD display with subpixel organisation from display top to bottom of B,G,R such that the vertical subpixel resolution is three times that of the full pixel vertical resolution (VBGR). |
static Object |
VALUE_TEXT_ANTIALIAS_LCD_VRGB
Text antialiasing hint value -- request that text be displayed optimised for an LCD display with subpixel organisation from display top to bottom of R,G,B such that the vertical subpixel resolution is three times that of the full pixel vertical resolution (VRGB). |
static Object |
VALUE_TEXT_ANTIALIAS_OFF
Text antialiasing hint value -- text rendering is done without any form of antialiasing. |
static Object |
VALUE_TEXT_ANTIALIAS_ON
Text antialiasing hint value -- text rendering is done with some form of antialiasing. |
Constructor Summary | |
---|---|
RenderingHints
(
Map
<
RenderingHints.Key
Constructs a new object with keys and values initialized from the specified Map object which |
|
RenderingHints
(
RenderingHints.Key
key,
Object
value) Constructs a new object with the specified key/value pair. |
Method Summary | |
---|---|
void |
add
(
RenderingHints
hints) Adds all of the keys and corresponding values from the specified RenderingHints object to this RenderingHints object. |
void |
clear
() Clears this RenderingHints object of all key/value pairs. |
Object |
clone
() Creates a clone of this RenderingHints object that has the same contents as this RenderingHints object. |
boolean |
containsKey
(
Object
key) Returns true if this RenderingHints contains a mapping for the specified key. |
boolean |
containsValue
(
Object
value) Returns true if this RenderingHints maps one or more keys to the specified value. |
Set < Map.Entry < Object , Object >> |
entrySet
() Returns a Set view of the mappings contained in this RenderingHints. |
boolean |
equals
(
Object
o) Compares the specified Object with this RenderingHints for equality. |
Object |
get
(
Object
key) Returns the value to which the specified key is mapped. |
int |
hashCode
() Returns the hash code value for this RenderingHints. |
boolean |
isEmpty
() Returns true if this RenderingHints contains no key-value mappings. |
Set < Object > |
keySet
() Returns a Set view of the Keys contained in this RenderingHints. |
Object |
put
(
Object
key,
Object
value) Maps the specified key to the specified value in this RenderingHints object. |
void |
putAll
(
Map
<?,?> m) Copies all of the mappings from the specified Map to this RenderingHints. |
Object |
remove
(
Object
key) Removes the key and its corresponding value from this RenderingHints object. |
int |
size
() Returns the number of key-value mappings in this RenderingHints. |
String |
toString
() Returns a rather long string representation of the hashmap which contains the mappings of keys to values for this RenderingHints object. |
Collection < Object > |
values
() Returns a Collection view of the values contained in this RenderinHints. |
Methods inherited from class java.lang. Object |
---|
finalize , getClass , notify , notifyAll , wait , wait , wait |
Field Detail |
---|
public static final RenderingHints.Key KEY_ANTIALIASING
A typical antialiasing algorithm works by blending the existing colors of the pixels along the boundary of a shape with the requested fill paint according to the estimated partial pixel coverage of the shape.
The allowable values for this hint are
public static final Object VALUE_ANTIALIAS_ON
public static final Object VALUE_ANTIALIAS_OFF
public static final Object VALUE_ANTIALIAS_DEFAULT
public static final RenderingHints.Key KEY_RENDERING
The allowable values for this hint are
public static final Object VALUE_RENDER_SPEED
public static final Object VALUE_RENDER_QUALITY
public static final Object VALUE_RENDER_DEFAULT
public static final RenderingHints.Key KEY_DITHERING
Some rendering destinations may support a limited number of color choices which may not be able to accurately represent the full spectrum of colors that can result during rendering operations. For such a destination the DITHERING hint controls whether rendering is done with a flat solid fill of a single pixel value which is the closest supported color to what was requested, or whether shapes will be filled with a pattern of colors which combine to better approximate that color.
The allowable values for this hint are
public static final Object VALUE_DITHER_DISABLE
public static final Object VALUE_DITHER_ENABLE
public static final Object VALUE_DITHER_DEFAULT
public static final RenderingHints.Key KEY_TEXT_ANTIALIASING
The allowable values for this hint are
public static final Object VALUE_TEXT_ANTIALIAS_ON
public static final Object VALUE_TEXT_ANTIALIAS_OFF
public static final Object VALUE_TEXT_ANTIALIAS_DEFAULT
public static final Object VALUE_TEXT_ANTIALIAS_GASP
TrueType fonts typically provide this information in the 'gasp' table. In the absence of this information, the behaviour for a particular font and size is determined by implementation defaults.
Note: A font designer will typically carefully hint a font for the most common user interface point sizes. Consequently the 'gasp' table will likely specify to use only hinting at those sizes and not "smoothing". So in many cases the resulting text display is equivalent to VALUE_TEXT_ANTIALIAS_OFF. This may be unexpected but is correct.
Logical fonts which are composed of multiple physical fonts will for consistency will use the setting most appropriate for the overall composite font.
public static final Object VALUE_TEXT_ANTIALIAS_LCD_HRGB
Notes:
An implementation when choosing whether to apply any of the LCD text hint values may take into account factors including requiring color depth of the destination to be at least 15 bits per pixel (ie 5 bits per color component), characteristics of a font such as whether embedded bitmaps may produce better results, or when displaying to a non-local networked display device enabling it only if suitable protocols are available, or ignoring the hint if performing very high resolution rendering or the target device is not appropriate: eg when printing.
These hints can equally be applied when rendering to software images, but these images may not then be suitable for general export, as the text will have been rendered appropriately for a specific subpixel organisation. Also lossy images are not a good choice, nor image formats such as GIF which have limited colors. So unless the image is destined solely for rendering on a display device with the same configuration, some other text anti-aliasing hint such as VALUE_TEXT_ANTIALIAS_ON may be a better choice.
Selecting a value which does not match the LCD display in use will likely lead to a degradation in text quality. On display devices (ie CRTs) which do not have the same characteristics as LCD displays, the overall effect may appear similar to standard text anti-aliasing, but the quality may be degraded by color distortion. Analog connected LCD displays may also show little advantage over standard text-antialiasing and be similar to CRTs.
In other words for the best results use an LCD display with a digital display connector and specify the appropriate sub-pixel configuration.
public static final Object VALUE_TEXT_ANTIALIAS_LCD_HBGR
public static final Object VALUE_TEXT_ANTIALIAS_LCD_VRGB
public static final Object VALUE_TEXT_ANTIALIAS_LCD_VBGR
public static final RenderingHints.Key KEY_TEXT_LCD_CONTRAST
public static final RenderingHints.Key KEY_FRACTIONALMETRICS
Rendering text to a low resolution device like a screen will necessarily involve a number of rounding operations as the high quality and very precise definition of the shape and metrics of the character glyphs must be matched to discrete device pixels. Ideally the positioning of glyphs during text layout would be calculated by scaling the design metrics in the font according to the point size, but then the scaled advance width will not necessarily be an integer number of pixels. If the glyphs are positioned with sub-pixel accuracy according to these scaled design metrics then the rasterization would ideally need to be adjusted for each possible sub-pixel origin.
Unfortunately, scaling each glyph customized to its exact subpixel origin during text layout would be prohibitively expensive so a simplified system based on integer device positions is typically used to lay out the text. The rasterization of the glyph and the scaled advance width are both adjusted together to yield text that looks good at device resolution and has consistent integer pixel distances between glyphs that help the glyphs look uniformly and consistently spaced and readable.
This process of rounding advance widths for rasterized glyphs to integer distances means that the character density and the overall length of a string of text will be different from the theoretical design measurements due to the accumulation of a series of small differences in the adjusted widths of each glyph. The specific differences will be different for each glyph, some being wider and some being narrower than their theoretical design measurements. Thus the overall difference in character density and length will vary by a number of factors including the font, the specific device resolution being targeted, and the glyphs chosen to represent the string being rendered. As a result, rendering the same string at multiple device resolutions can yield widely varying metrics for whole strings.
When FRACTIONALMETRICS are enabled, the true font design metrics are scaled by the point size and used for layout with sub-pixel accuracy. The average density of glyphs and total length of a long string of characters will therefore more closely match the theoretical design of the font, but readability may be affected since individual pairs of characters may not always appear to be consistent distances apart depending on how the sub-pixel accumulation of the glyph origins meshes with the device pixel grid. Enabling this hint may be desirable when text layout is being performed that must be consistent across a wide variety of output resolutions. Specifically, this hint may be desirable in situations where the layout of text is being previewed on a low resolution device like a screen for output that will eventually be rendered on a high resolution printer or typesetting device.
When disabled, the scaled design metrics are rounded or adjusted to integer distances for layout. The distances between any specific pair of glyphs will be more uniform on the device, but the density and total length of long strings may no longer match the theoretical intentions of the font designer. Disabling this hint will typically produce more readable results on low resolution devices like computer monitors.
The allowable values for this key are
public static final Object VALUE_FRACTIONALMETRICS_OFF
public static final Object VALUE_FRACTIONALMETRICS_ON
public static final Object VALUE_FRACTIONALMETRICS_DEFAULT
public static final RenderingHints.Key KEY_INTERPOLATION
Implicitly images are defined to provide color samples at integer coordinate locations. When images are rendered upright with no scaling onto a destination, the choice of which image pixels map to which device pixels is obvious and the samples at the integer coordinate locations in the image are transfered to the pixels at the corresponding integer locations on the device pixel grid one for one. When images are rendered in a scaled, rotated, or otherwise transformed coordinate system, then the mapping of device pixel coordinates back to the image can raise the question of what color sample to use for the continuous coordinates that lie between the integer locations of the provided image samples. Interpolation algorithms define functions which provide a color sample for any continuous coordinate in an image based on the color samples at the surrounding integer coordinates.
The allowable values for this hint are
public static final Object VALUE_INTERPOLATION_NEAREST_NEIGHBOR
As the image is scaled up, it will look correspondingly blocky. As the image is scaled down, the colors for source pixels will be either used unmodified, or skipped entirely in the output representation.
public static final Object VALUE_INTERPOLATION_BILINEAR
As the image is scaled up, there are no blocky edges between the colors in the image as there are with NEAREST_NEIGHBOR , but the blending may show some subtle discontinuities along the horizontal and vertical edges that line up with the samples caused by a sudden change in the slope of the interpolation from one side of a sample to the other. As the image is scaled down, more image pixels have their color samples represented in the resulting output since each output pixel recieves color information from up to 4 image pixels.
public static final Object VALUE_INTERPOLATION_BICUBIC
As the image is scaled up, there are no blocky edges and the interpolation should appear smoother and with better depictions of any edges in the original image than with BILINEAR. As the image is scaled down, even more of the original color samples from the original image will have their color information carried through and represented.
public static final RenderingHints.Key KEY_ALPHA_INTERPOLATION
This hint could control the choice of alpha blending calculations that sacrifice some precision to use fast lookup tables or lower precision SIMD instructions. This hint could also control whether or not the color and alpha values are converted into a linear color space during the calculations for a more linear visual effect at the expense of additional per-pixel calculations.
The allowable values for this hint are
public static final Object VALUE_ALPHA_INTERPOLATION_SPEED
public static final Object VALUE_ALPHA_INTERPOLATION_QUALITY
public static final Object VALUE_ALPHA_INTERPOLATION_DEFAULT
public static final RenderingHints.Key KEY_COLOR_RENDERING
When a rendering or image manipulation operation produces a color value that must be stored into a destination, it must first convert that color into a form suitable for storing into the destination image or surface. Minimally, the color components must be converted to bit representations and ordered in the correct order or an index into a color lookup table must be chosen before the data can be stored into the destination memory. Without this minimal conversion, the data in the destination would likely represent random, incorrect or possibly even unsupported values. Algorithms to quickly convert the results of rendering operations into the color format of most common destinations are well known and fairly optimal to execute.
Simply performing the most basic color format conversion to store colors into a destination can potentially ignore a difference in the calibration of the ColorSpace of the source and destination or other factors such as the linearity of the gamma correction. Unless the source and destination ColorSpace are identical, to correctly perform a rendering operation with the most care taken for the accuracy of the colors being represented, the source colors should be converted to a device independent ColorSpace and the results then converted back to the destination ColorSpace. Furthermore, if calculations such as the blending of multiple source colors are to be performed during the rendering operation, greater visual clarity can be achieved if the intermediate device independent ColorSpace is chosen to have a linear relationship between the values being calculated and the perception of the human eye to the response curves of the output device.
The allowable values for this hint are
public static final Object VALUE_COLOR_RENDER_SPEED
public static final Object VALUE_COLOR_RENDER_QUALITY
public static final Object VALUE_COLOR_RENDER_DEFAULT
public static final RenderingHints.Key KEY_STROKE_CONTROL
Some implementations may be able to use an optimized platform rendering library which may be faster than traditional software rendering algorithms on a given platform, but which may also not support floating point coordinates. Some implementations may also have sophisticated algorithms which perturb the coordinates of a path so that wide lines appear more uniform in width and spacing.
If an implementation performs any type of modification or "normalization" of a path, it should never move the coordinates by more than half a pixel in any direction.
The allowable values for this hint are
public static final Object VALUE_STROKE_DEFAULT
public static final Object VALUE_STROKE_NORMALIZE
public static final Object VALUE_STROKE_PURE
Constructor Detail |
---|
public RenderingHints(Map<RenderingHints.Key,?> init)
public RenderingHints(RenderingHints.Key key, Object value)
Method Detail |
---|
public int size()
public boolean isEmpty()
public boolean containsKey(Object key)
public boolean containsValue(Object value)
(value==null ? v==null : value.equals(v)). This operation will probably require time linear in the RenderingHints size for most implementations of RenderingHints.
public Object get(Object key)
public Object put(Object key, Object value)
public void add(RenderingHints hints)
public void clear()
public Object remove(Object key)
public void putAll(Map<?,?> m)
public Set<Object> keySet()
public Collection<Object> values()
public Set<Map.Entry<Object,Object>> entrySet()
The entrySet returned from a RenderingHints object is not modifiable.
public boolean equals(Object o)
(t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))). This ensures that the equals method works properly across different implementations of the Map interface.
public int hashCode()
public Object clone()
public String toString()