com.sun.opengl.util.texture

## Class Texture

- java.lang.Object
- - com.sun.opengl.util.texture.Texture

    public class Texture
    extends Object

Represents an OpenGL texture object. Contains convenience routines for enabling/disabling OpenGL texture state, binding this texture, and computing texture coordinates for both the entire image as well as a sub-image.

Non-power-of-two restrictions
When creating an OpenGL texture object, the Texture class will attempt to leverage the GL_ARB_texture_non_power_of_two and GL_ARB_texture_rectangle extensions (in that order) whenever possible. If neither extension is available, the Texture class will simply upload a non-pow2-sized image into a standard pow2-sized texture (without any special scaling). Since the choice of extension (or whether one is used at all) depends on the user's machine configuration, developers are recommended to use `getImageTexCoords()` and `getSubImageTexCoords(int, int, int, int)`, as those methods will calculate the appropriate texture coordinates for the situation.

One caveat in this approach is that certain texture wrap modes (e.g. `GL_REPEAT`) are not legal when the GL_ARB_texture_rectangle extension is in use. Another issue to be aware of is that in the default pow2 scenario, if the original image does not have pow2 dimensions, then wrapping may not work as one might expect since the image does not extend to the edges of the pow2 texture. If texture wrapping is important, it is recommended to use only pow2-sized images with the Texture class.

Performance Tips
For best performance, try to avoid calling `enable()` / `bind()` / `disable()` any more than necessary. For example, applications using many Texture objects in the same scene may want to reduce the number of calls to both `enable()` and `disable()`. To do this it is necessary to call `getTarget()` to make sure the OpenGL texture target is the same for all of the Texture objects in use; non-power-of-two textures using the GL_ARB_texture_rectangle extension use a different target than power-of-two textures using the GL_TEXTURE_2D target. Note that when switching between textures it is necessary to call `bind()`, but when drawing many triangles all using the same texture, for best performance only one call to `bind()` should be made.

Alpha premultiplication and blending
The mathematically correct way to perform blending in OpenGL (with the SrcOver "source over destination" mode, or any other Porter-Duff rule) is to use "premultiplied color components", which means the R/G/ B color components have already been multiplied by the alpha value. To make things easier for developers, the Texture class will automatically convert non-premultiplied image data into premultiplied data when storing it into an OpenGL texture. As a result, it is important to use the correct blending function; for example, the SrcOver rule is expressed as:

        gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE_MINUS_SRC_ALPHA);

Also, when using a texture function like `GL_MODULATE` where the current color plays a role, it is important to remember to make sure that the color is specified in a premultiplied form, for example:

        float a = ...;
        float r = r * a;
        float g = g * a;
        float b = b * a;
        gl.glColor4f(r, g, b, a);

For reference, here is a list of the Porter-Duff compositing rules and the associated OpenGL blend functions (source and destination factors) to use in the face of premultiplied alpha:

Rule | Source | Dest
Clear | GL_ZERO | GL_ZERO
Src | GL_ONE | GL_ZERO
SrcOver | GL_ONE | GL_ONE_MINUS_SRC_ALPHA
DstOver | GL_ONE_MINUS_DST_ALPHA | GL_ONE
SrcIn | GL_DST_ALPHA | GL_ZERO
DstIn | GL_ZERO | GL_SRC_ALPHA
SrcOut | GL_ONE_MINUS_DST_ALPHA | GL_ZERO
DstOut | GL_ZERO | GL_ONE_MINUS_SRC_ALPHA
Dst | GL_ZERO | GL_ONE
SrcAtop | GL_DST_ALPHA | GL_ONE_MINUS_SRC_ALPHA
DstAtop | GL_ONE_MINUS_DST_ALPHA | GL_SRC_ALPHA
AlphaXor | GL_ONE_MINUS_DST_ALPHA | GL_ONE_MINUS_SRC_ALPHA

Author:
  Chris Campbell, Kenneth Russell

### Method Summary

Methods
`void` `bind()` Binds this texture to the current GL context.
`void` `disable()` Disables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state.
`void` `dispose()` Disposes the native resources used by this texture object.
`void` `enable()` Enables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state.
`float` `getAspectRatio()` Returns the original aspect ratio of the image, defined as (image width) / (image height), before any scaling that might have occurred as a result of using the GLU mipmap routines.
`int` `getEstimatedMemorySize()` Returns an estimate of the amount of texture memory in bytes this Texture consumes.
`int` `getHeight()` Returns the height of the allocated OpenGL texture in pixels.
`int` `getImageHeight()` Returns the height of the image contained within this texture.
`TextureCoords` `getImageTexCoords()` Returns the set of texture coordinates corresponding to the entire image.
`int` `getImageWidth()` Returns the width of the image contained within this texture.
`boolean` `getMustFlipVertically()` Indicates whether this texture's texture coordinates must be flipped vertically in order to properly display the texture.
`TextureCoords` `getSubImageTexCoords(int x1, int y1, int x2, int y2)` Returns the set of texture coordinates corresponding to the specified sub-image.
`int` `getTarget()` Returns the OpenGL "target" of this texture.
`int` `getTextureObject()` Returns the underlying OpenGL texture object for this texture.
`int` `getWidth()` Returns the width of the allocated OpenGL texture in pixels.
`boolean` `isUsingAutoMipmapGeneration()` Indicates whether this Texture is using automatic mipmap generation (via the OpenGL texture parameter GL_GENERATE_MIPMAP).
`void` `setTexParameterf(int parameterName, float value)` Sets the OpenGL floating-point texture parameter for the texture's target.
`void` `setTexParameterfv(int parameterName, float[] params, int params_offset)` Sets the OpenGL multi-floating-point texture parameter for the texture's target.
`void` `setTexParameterfv(int parameterName, FloatBuffer params)` Sets the OpenGL multi-floating-point texture parameter for the texture's target.
`void` `setTexParameteri(int parameterName, int value)` Sets the OpenGL integer texture parameter for the texture's target.
`void` `setTexParameteriv(int parameterName, int[] params, int params_offset)` Sets the OpenGL multi-integer texture parameter for the texture's target.
`void` `setTexParameteriv(int parameterName, IntBuffer params)` Sets the OpenGL multi-integer texture parameter for the texture's target.
`void` `updateImage(TextureData data)` Updates the entire content area of this texture using the data in the given image.
`void` `updateImage(TextureData data, int target)` Updates the content area of the specified target of this texture using the data in the given image.
`void` `updateSubImage(TextureData data, int mipmapLevel, int x, int y)` Updates a subregion of the content area of this texture using the given data.
`void` `updateSubImage(TextureData data, int mipmapLevel, int dstx, int dsty, int srcx, int srcy, int width, int height)` Updates a subregion of the content area of this texture using the specified sub-region of the given data.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Method Detail

#### enable

    public void enable()
                throws GLException

Enables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state. This method is a shorthand equivalent of the following OpenGL code:

        gl.glEnable(texture.getTarget());

See the performance tips above for hints on how to maximize performance when using many Texture objects.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### disable

    public void disable()
                 throws GLException

Disables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state. This method is a shorthand equivalent of the following OpenGL code:

        gl.glDisable(texture.getTarget());

See the performance tips above for hints on how to maximize performance when using many Texture objects.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### bind

    public void bind()
              throws GLException

Binds this texture to the current GL context. This method is a shorthand equivalent of the following OpenGL code:

        gl.glBindTexture(texture.getTarget(), texture.getTextureObject());

See the performance tips above for hints on how to maximize performance when using many Texture objects.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### dispose

    public void dispose()
                 throws GLException

Disposes the native resources used by this texture object.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### getTarget

    public int getTarget()

Returns the OpenGL "target" of this texture.

Returns:
  the OpenGL target of this texture
See Also:
  `GL.GL_TEXTURE_2D`, `GL.GL_TEXTURE_RECTANGLE_ARB`

#### getWidth

    public int getWidth()

Returns the width of the allocated OpenGL texture in pixels. Note that the texture width will be greater than or equal to the width of the image contained within.

Returns:
  the width of the texture

#### getHeight

    public int getHeight()

Returns the height of the allocated OpenGL texture in pixels. Note that the texture height will be greater than or equal to the height of the image contained within.

Returns:
  the height of the texture

#### getImageWidth

    public int getImageWidth()

Returns the width of the image contained within this texture. Note that for non-power-of-two textures in particular this may not be equal to the result of `getWidth()`. It is recommended that applications call `getImageTexCoords()` and `getSubImageTexCoords(int, int, int, int)` rather than using this API directly.

Returns:
  the width of the image

#### getImageHeight

    public int getImageHeight()

Returns the height of the image contained within this texture. Note that for non-power-of-two textures in particular this may not be equal to the result of `getHeight()`. It is recommended that applications call `getImageTexCoords()` and `getSubImageTexCoords(int, int, int, int)` rather than using this API directly.

Returns:
  the height of the image

#### getAspectRatio

    public float getAspectRatio()

Returns the original aspect ratio of the image, defined as (image width) / (image height), before any scaling that might have occurred as a result of using the GLU mipmap routines.

#### getImageTexCoords

    public TextureCoords getImageTexCoords()

Returns the set of texture coordinates corresponding to the entire image. If the TextureData indicated that the texture coordinates must be flipped vertically, the returned TextureCoords will take that into account.

Returns:
  the texture coordinates corresponding to the entire image

#### getSubImageTexCoords

    public TextureCoords getSubImageTexCoords(int x1,
                                     int y1,
                                     int x2,
                                     int y2)

Returns the set of texture coordinates corresponding to the specified sub-image. The (x1, y1) and (x2, y2) points are specified in terms of pixels starting from the lower-left of the image. (x1, y1) should specify the lower-left corner of the sub-image and (x2, y2) the upper-right corner of the sub-image. If the TextureData indicated that the texture coordinates must be flipped vertically, the returned TextureCoords will take that into account; this should not be handled by the end user in the specification of the y1 and y2 coordinates.

Returns:
  the texture coordinates corresponding to the specified sub-image

#### updateImage

    public void updateImage(TextureData data)
                     throws GLException

Updates the entire content area of this texture using the data in the given image.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### getMustFlipVertically

    public boolean getMustFlipVertically()

Indicates whether this texture's texture coordinates must be flipped vertically in order to properly display the texture. This is handled automatically by `getImageTexCoords` and `getSubImageTexCoords`, but applications may generate or otherwise produce texture coordinates which must be corrected.

#### updateImage

    public void updateImage(TextureData data,
                   int target)
                     throws GLException

Updates the content area of the specified target of this texture using the data in the given image. In general this is intended for construction of cube maps.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### updateSubImage

    public void updateSubImage(TextureData data,
                      int mipmapLevel,
                      int x,
                      int y)
                        throws GLException

Updates a subregion of the content area of this texture using the given data. If automatic mipmap generation is in use (see `isUsingAutoMipmapGeneration`), updates to the base (level 0) mipmap will cause the lower-level mipmaps to be regenerated, and updates to other mipmap levels will be ignored. Otherwise, if automatic mipmap generation is not in use, only updates the specified mipmap level and does not re-generate mipmaps if they were originally produced or loaded.

Parameters:
  `data` - the image data to be uploaded to this texture
  `mipmapLevel` - the mipmap level of the texture to set. If this is non-zero and the TextureData contains mipmap data, the appropriate mipmap level will be selected.
  `x` - the x offset (in pixels) relative to the lower-left corner of this texture
  `y` - the y offset (in pixels) relative to the lower-left corner of this texture
Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### updateSubImage

    public void updateSubImage(TextureData data,
                      int mipmapLevel,
                      int dstx,
                      int dsty,
                      int srcx,
                      int srcy,
                      int width,
                      int height)
                        throws GLException

Updates a subregion of the content area of this texture using the specified sub-region of the given data. If automatic mipmap generation is in use (see `isUsingAutoMipmapGeneration`), updates to the base (level 0) mipmap will cause the lower-level mipmaps to be regenerated, and updates to other mipmap levels will be ignored. Otherwise, if automatic mipmap generation is not in use, only updates the specified mipmap level and does not re-generate mipmaps if they were originally produced or loaded. This method is only supported for uncompressed TextureData sources.

Parameters:
  `data` - the image data to be uploaded to this texture
  `mipmapLevel` - the mipmap level of the texture to set. If this is non-zero and the TextureData contains mipmap data, the appropriate mipmap level will be selected.
  `dstx` - the x offset (in pixels) relative to the lower-left corner of this texture where the update will be applied
  `dsty` - the y offset (in pixels) relative to the lower-left corner of this texture where the update will be applied
  `srcx` - the x offset (in pixels) relative to the lower-left corner of the supplied TextureData from which to fetch the update rectangle
  `srcy` - the y offset (in pixels) relative to the lower-left corner of the supplied TextureData from which to fetch the update rectangle
  `width` - the width (in pixels) of the rectangle to be updated
  `height` - the height (in pixels) of the rectangle to be updated
Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameterf

    public void setTexParameterf(int parameterName,
                        float value)

Sets the OpenGL floating-point texture parameter for the texture's target. This gives control over parameters such as GL_TEXTURE_MAX_ANISOTROPY_EXT. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameterfv

    public void setTexParameterfv(int parameterName,
                         FloatBuffer params)

Sets the OpenGL multi-floating-point texture parameter for the texture's target. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameterfv

    public void setTexParameterfv(int parameterName,
                         float[] params,
                         int params_offset)

Sets the OpenGL multi-floating-point texture parameter for the texture's target. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameteri

    public void setTexParameteri(int parameterName,
                        int value)

Sets the OpenGL integer texture parameter for the texture's target. This gives control over parameters such as GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, which by default are set to GL_CLAMP_TO_EDGE if OpenGL 1.2 is supported on the current platform and GL_CLAMP if not. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameteriv

    public void setTexParameteriv(int parameterName,
                         IntBuffer params)

Sets the OpenGL multi-integer texture parameter for the texture's target. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### setTexParameteriv

    public void setTexParameteriv(int parameterName,
                         int[] params,
                         int params_offset)

Sets the OpenGL multi-integer texture parameter for the texture's target. Causes this texture to be bound to the current texture state.

Throws:
  `GLException` - if no OpenGL context was current or if any OpenGL-related errors occurred

#### getTextureObject

    public int getTextureObject()

Returns the underlying OpenGL texture object for this texture. Most applications will not need to access this, since it is handled automatically by the bind() and dispose() APIs.

#### getEstimatedMemorySize

    public int getEstimatedMemorySize()

Returns an estimate of the amount of texture memory in bytes this Texture consumes. It should only be treated as an estimate; most applications should not need to query this but instead let the OpenGL implementation page textures in and out as necessary.

#### isUsingAutoMipmapGeneration

    public boolean isUsingAutoMipmapGeneration()

Indicates whether this Texture is using automatic mipmap generation (via the OpenGL texture parameter GL_GENERATE_MIPMAP). This will automatically be used when mipmapping is requested via the TextureData and either OpenGL 1.4 or the GL_SGIS_generate_mipmap extension is available. If so, updates to the base image (mipmap level 0) will automatically propagate down to the lower mipmap levels. Manual updates of the mipmap data at these lower levels will be ignored.