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#619: Fix WebP Y'CbCr->RGB conversion (now uses rec 601)

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Harald Kuhr
2021-08-26 16:47:51 +02:00
parent 6daca00fcd
commit 976e5d6210
9 changed files with 120 additions and 63 deletions
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118
imageio/imageio-core/src/main/java/com/twelvemonkeys/imageio/color/YCbCrConverter.java
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@@ -45,36 +45,82 @@ public final class YCbCrConverter {
private final static int CENTERJSAMPLE = 128;
private final static int ONE_HALF = 1 << (SCALEBITS - 1);
private final static int[] Cr_R_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_B_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cr_G_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_G_LUT = new int[MAXJSAMPLE + 1];
private final static class JPEG {
private final static int[] Cr_R_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_B_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cr_G_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_G_LUT = new int[MAXJSAMPLE + 1];
/**
* Initializes tables for YCC->RGB color space conversion.
*/
private static void buildYCCtoRGBtable() {
if (ColorSpaces.DEBUG) {
System.err.println("Building YCC conversion table");
/**
* Initializes tables for YCC->RGB color space conversion.
*/
private static void buildYCCtoRGBtable() {
if (ColorSpaces.DEBUG) {
System.err.println("Building JPEG YCbCr conversion table");
}
for (int i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
// i is the actual input pixel value, in the range 0..MAXJSAMPLE
// The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE
// Cr=>R value is nearest int to 1.40200 * x
Cr_R_LUT[i] = (int) ((1.40200 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cb=>B value is nearest int to 1.77200 * x
Cb_B_LUT[i] = (int) ((1.77200 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cr=>G value is scaled-up -0.71414 * x
Cr_G_LUT[i] = -(int) (0.71414 * (1 << SCALEBITS) + 0.5) * x;
// Cb=>G value is scaled-up -0.34414 * x
// We also add in ONE_HALF so that need not do it in inner loop
Cb_G_LUT[i] = -(int) ((0.34414) * (1 << SCALEBITS) + 0.5) * x + ONE_HALF;
}
}
for (int i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
// i is the actual input pixel value, in the range 0..MAXJSAMPLE
// The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE
// Cr=>R value is nearest int to 1.40200 * x
Cr_R_LUT[i] = (int) ((1.40200 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cb=>B value is nearest int to 1.77200 * x
Cb_B_LUT[i] = (int) ((1.77200 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cr=>G value is scaled-up -0.71414 * x
Cr_G_LUT[i] = -(int) (0.71414 * (1 << SCALEBITS) + 0.5) * x;
// Cb=>G value is scaled-up -0.34414 * x
// We also add in ONE_HALF so that need not do it in inner loop
Cb_G_LUT[i] = -(int) ((0.34414) * (1 << SCALEBITS) + 0.5) * x + ONE_HALF;
static {
buildYCCtoRGBtable();
}
}
static {
buildYCCtoRGBtable();
private final static class ITU_R_601 {
private final static int[] Cr_R_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_B_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cr_G_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Cb_G_LUT = new int[MAXJSAMPLE + 1];
private final static int[] Y_LUT = new int[MAXJSAMPLE + 1];
/**
* Initializes tables for YCC->RGB color space conversion.
*/
private static void buildYCCtoRGBtable() {
if (ColorSpaces.DEBUG) {
System.err.println("Building ITU-R REC.601 YCbCr conversion table");
}
for (int i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
// i is the actual input pixel value, in the range 0..MAXJSAMPLE
// The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE
// Y'CbCr to RGB conversion, using values from BT.601 specification:
// R = 1.16438 * (Y'-16) + 1.59603 * (Cr-128)
// G = 1.16438 * (Y'-16) - 0.39176 * (Cb-128) - 0.81297 * (Cr-128)
// B = 1.16438 * (Y'-16) + 2.01723 * (Cb-128)
// Cr=>R value is nearest int to 1.59603 * x
Cr_R_LUT[i] = ((int) (1.59603 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cb=>B value is nearest int to 2.01723 * x
Cb_B_LUT[i] = ((int) (2.01723 * (1 << SCALEBITS) + 0.5) * x + ONE_HALF) >> SCALEBITS;
// Cr=>G value is scaled-up -0.81297 * x
Cr_G_LUT[i] = -(int) (0.81297 * (1 << SCALEBITS) + 0.5) * x;
// Cb=>G value is scaled-up -0.39176 * x
// We also add in ONE_HALF so that need not do it in inner loop
Cb_G_LUT[i] = -(int) ((0.39176) * (1 << SCALEBITS) + 0.5) * x + ONE_HALF;
// Y`=>RGB
Y_LUT[i] = ((int) (1.16438 * (1 << SCALEBITS) + 0.5) * (i - 16) + ONE_HALF) >> SCALEBITS;
}
}
static {
buildYCCtoRGBtable();
}
}
public static void convertYCbCr2RGB(final byte[] yCbCr, final byte[] rgb, final double[] coefficients, double[] referenceBW, final int offset) {
@@ -108,17 +154,27 @@ public final class YCbCrConverter {
rgb[offset + 1] = clamp(green);
}
public static void convertYCbCr2RGB(final byte[] yCbCr, final byte[] rgb, final int offset) {
int y = yCbCr[offset] & 0xff;
int cr = yCbCr[offset + 2] & 0xff;
public static void convertJPEGYCbCr2RGB(final byte[] yCbCr, final byte[] rgb, final int offset) {
int y = yCbCr[offset ] & 0xff;
int cb = yCbCr[offset + 1] & 0xff;
int cr = yCbCr[offset + 2] & 0xff;
rgb[offset] = clamp(y + Cr_R_LUT[cr]);
rgb[offset + 1] = clamp(y + (Cb_G_LUT[cb] + Cr_G_LUT[cr] >> SCALEBITS));
rgb[offset + 2] = clamp(y + Cb_B_LUT[cb]);
rgb[offset ] = clamp(y + JPEG.Cr_R_LUT[cr]);
rgb[offset + 1] = clamp(y + (JPEG.Cb_G_LUT[cb] + JPEG.Cr_G_LUT[cr] >> SCALEBITS));
rgb[offset + 2] = clamp(y + JPEG.Cb_B_LUT[cb]);
}
private static byte clamp(int val) {
public static void convertRec601YCbCr2RGB(final byte[] yCbCr, final byte[] rgb, final int offset) {
int y = yCbCr[offset ] & 0xff;
int cb = yCbCr[offset + 1] & 0xff;
int cr = yCbCr[offset + 2] & 0xff;
rgb[offset ] = clamp(ITU_R_601.Y_LUT[y] + ITU_R_601.Cr_R_LUT[cr]);
rgb[offset + 1] = clamp(ITU_R_601.Y_LUT[y] + (ITU_R_601.Cr_G_LUT[cr] + ITU_R_601.Cb_G_LUT[cb] >> SCALEBITS));
rgb[offset + 2] = clamp(ITU_R_601.Y_LUT[y] + ITU_R_601.Cb_B_LUT[cb]);
}
private static byte clamp(final int val) {
return (byte) Math.max(0, Math.min(255, val));
}
}