The Independent JPEG Group's JPEG software v1
diff --git a/jdcolor.c b/jdcolor.c
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--- /dev/null
+++ b/jdcolor.c
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+/*
+ * jdcolor.c
+ *
+ * Copyright (C) 1991, Thomas G. Lane.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains output colorspace conversion routines.
+ * These routines are invoked via the methods color_convert
+ * and colorout_init/term.
+ */
+
+#include "jinclude.h"
+
+
+/*
+ * Initialize for colorspace conversion.
+ */
+
+METHODDEF void
+colorout_init (decompress_info_ptr cinfo)
+{
+ /* no work needed */
+}
+
+
+/*
+ * Convert some rows of samples to the output colorspace.
+ * This version handles YCbCr -> RGB conversion.
+ * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
+ * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
+ */
+
+METHODDEF void
+ycc_rgb_convert (decompress_info_ptr cinfo, int num_rows,
+ JSAMPIMAGE input_data, JSAMPIMAGE output_data)
+{
+ register INT32 y, u, v, x;
+ register JSAMPROW inptr0, inptr1, inptr2;
+ register JSAMPROW outptr0, outptr1, outptr2;
+ register long col;
+ register long width = cinfo->image_width;
+ register int row;
+
+ for (row = 0; row < num_rows; row++) {
+ inptr0 = input_data[0][row];
+ inptr1 = input_data[1][row];
+ inptr2 = input_data[2][row];
+ outptr0 = output_data[0][row];
+ outptr1 = output_data[1][row];
+ outptr2 = output_data[2][row];
+ for (col = width; col > 0; col--) {
+ y = GETJSAMPLE(*inptr0++);
+ u = (int) GETJSAMPLE(*inptr1++) - CENTERJSAMPLE;
+ v = (int) GETJSAMPLE(*inptr2++) - CENTERJSAMPLE;
+ /* Note: if the inputs were computed directly from RGB values,
+ * range-limiting would be unnecessary here; but due to possible
+ * noise in the DCT/IDCT phase, we do need to apply range limits.
+ */
+ y *= 1024; /* in case compiler can't spot common subexpression */
+ x = y + 1436*v + 512; /* red */
+ if (x < 0) x = 0;
+ if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
+ *outptr0++ = x >> 10;
+ x = y - 352*u - 731*v + 512; /* green */
+ if (x < 0) x = 0;
+ if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
+ *outptr1++ = x >> 10;
+ x = y + 1815*u + 512; /* blue */
+ if (x < 0) x = 0;
+ if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
+ *outptr2++ = x >> 10;
+ }
+ }
+}
+
+
+/*
+ * Color conversion for no colorspace change: just copy the data.
+ */
+
+METHODDEF void
+null_convert (decompress_info_ptr cinfo, int num_rows,
+ JSAMPIMAGE input_data, JSAMPIMAGE output_data)
+{
+ short ci;
+
+ for (ci = 0; ci < cinfo->num_components; ci++) {
+ jcopy_sample_rows(input_data[ci], 0, output_data[ci], 0,
+ num_rows, cinfo->image_width);
+ }
+}
+
+
+/*
+ * Color conversion for grayscale: just copy the data.
+ * This also works for YCbCr/YIQ -> grayscale conversion, in which
+ * we just copy the Y (luminance) component and ignore chrominance.
+ */
+
+METHODDEF void
+grayscale_convert (decompress_info_ptr cinfo, int num_rows,
+ JSAMPIMAGE input_data, JSAMPIMAGE output_data)
+{
+ jcopy_sample_rows(input_data[0], 0, output_data[0], 0,
+ num_rows, cinfo->image_width);
+}
+
+
+/*
+ * Finish up at the end of the file.
+ */
+
+METHODDEF void
+colorout_term (decompress_info_ptr cinfo)
+{
+ /* no work needed */
+}
+
+
+/*
+ * The method selection routine for output colorspace conversion.
+ */
+
+GLOBAL void
+jseldcolor (decompress_info_ptr cinfo)
+{
+ /* Make sure num_components agrees with jpeg_color_space */
+ switch (cinfo->jpeg_color_space) {
+ case CS_GRAYSCALE:
+ if (cinfo->num_components != 1)
+ ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
+ break;
+
+ case CS_RGB:
+ case CS_YIQ:
+ case CS_YCbCr:
+ if (cinfo->num_components != 3)
+ ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
+ break;
+
+ case CS_CMYK:
+ if (cinfo->num_components != 4)
+ ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
+ break;
+
+ default:
+ ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace");
+ break;
+ }
+
+ /* Set color_out_comps and conversion method based on requested space */
+ switch (cinfo->out_color_space) {
+ case CS_GRAYSCALE:
+ cinfo->color_out_comps = 1;
+ if (cinfo->jpeg_color_space == CS_GRAYSCALE ||
+ cinfo->jpeg_color_space == CS_YCbCr ||
+ cinfo->jpeg_color_space == CS_YIQ)
+ cinfo->methods->color_convert = grayscale_convert;
+ else
+ ERREXIT(cinfo->emethods, "Unsupported color conversion request");
+ break;
+
+ case CS_RGB:
+ cinfo->color_out_comps = 3;
+ if (cinfo->jpeg_color_space == CS_YCbCr)
+ cinfo->methods->color_convert = ycc_rgb_convert;
+ else if (cinfo->jpeg_color_space == CS_RGB)
+ cinfo->methods->color_convert = null_convert;
+ else
+ ERREXIT(cinfo->emethods, "Unsupported color conversion request");
+ break;
+
+ case CS_CMYK:
+ cinfo->color_out_comps = 4;
+ if (cinfo->jpeg_color_space == CS_CMYK)
+ cinfo->methods->color_convert = null_convert;
+ else
+ ERREXIT(cinfo->emethods, "Unsupported color conversion request");
+ break;
+
+ default:
+ ERREXIT(cinfo->emethods, "Unsupported output colorspace");
+ break;
+ }
+
+ if (cinfo->quantize_colors)
+ cinfo->final_out_comps = 1; /* single colormapped output component */
+ else
+ cinfo->final_out_comps = cinfo->color_out_comps;
+
+ cinfo->methods->colorout_init = colorout_init;
+ cinfo->methods->colorout_term = colorout_term;
+}
