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TurboJPEG: Add alpha offset array/method

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Also, set the red/green/blue offsets for TJPF_GRAY to -1 rather than 0.
It was undefined behavior for an application to use those arrays/methods
with TJPF_GRAY anyhow, and this makes it easier for applications to
programmatically detect whether a given pixel format has red, green, and
blue components.
This commit is contained in:
DRC
2017-11-16 20:43:12 -06:00
parent aa7459050d
commit dc4b900223
26 changed files with 265 additions and 81 deletions
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37
java/org/libjpegturbo/turbojpeg/TJ.java
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@@ -235,7 +235,8 @@ public final class TJ {
*
* @param pixelFormat the pixel format (one of <code>PF_*</code>)
*
* @return the red offset for the given pixel format.
* @return the red offset for the given pixel format, or -1 if the pixel
* format does not have a red component.
*/
public static int getRedOffset(int pixelFormat) {
checkPixelFormat(pixelFormat);
@@ -243,7 +244,7 @@ public final class TJ {
}
private static final int[] redOffset = {
0, 2, 0, 2, 3, 1, 0, 0, 2, 3, 1, -1
0, 2, 0, 2, 3, 1, -1, 0, 2, 3, 1, -1
};
@@ -256,7 +257,8 @@ public final class TJ {
*
* @param pixelFormat the pixel format (one of <code>PF_*</code>)
*
* @return the green offset for the given pixel format.
* @return the green offset for the given pixel format, or -1 if the pixel
* format does not have a green component.
*/
public static int getGreenOffset(int pixelFormat) {
checkPixelFormat(pixelFormat);
@@ -264,7 +266,7 @@ public final class TJ {
}
private static final int[] greenOffset = {
1, 1, 1, 1, 2, 2, 0, 1, 1, 2, 2, -1
1, 1, 1, 1, 2, 2, -1, 1, 1, 2, 2, -1
};
@@ -277,7 +279,8 @@ public final class TJ {
*
* @param pixelFormat the pixel format (one of <code>PF_*</code>)
*
* @return the blue offset for the given pixel format.
* @return the blue offset for the given pixel format, or -1 if the pixel
* format does not have a blue component.
*/
public static int getBlueOffset(int pixelFormat) {
checkPixelFormat(pixelFormat);
@@ -285,7 +288,29 @@ public final class TJ {
}
private static final int[] blueOffset = {
2, 0, 2, 0, 1, 3, 0, 2, 0, 1, 3, -1
2, 0, 2, 0, 1, 3, -1, 2, 0, 1, 3, -1
};
/**
* For the given pixel format, returns the number of bytes that the alpha
* component is offset from the start of the pixel. For instance, if a pixel
* of format <code>TJ.PF_BGRA</code> is stored in <code>char pixel[]</code>,
* then the alpha component will be
* <code>pixel[TJ.getAlphaOffset(TJ.PF_BGRA)]</code>.
*
* @param pixelFormat the pixel format (one of <code>PF_*</code>)
*
* @return the alpha offset for the given pixel format, or -1 if the pixel
* format does not have a alpha component.
*/
public static int getAlphaOffset(int pixelFormat) {
checkPixelFormat(pixelFormat);
return alphaOffset[pixelFormat];
}
private static final int[] alphaOffset = {
-1, -1, -1, -1, -1, -1, -1, 3, 3, 0, 0, -1
};