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-rw-r--r--src/mesa/swrast/s_readpix.c71
1 files changed, 45 insertions, 26 deletions
diff --git a/src/mesa/swrast/s_readpix.c b/src/mesa/swrast/s_readpix.c
index 334dc02918..78441bff38 100644
--- a/src/mesa/swrast/s_readpix.c
+++ b/src/mesa/swrast/s_readpix.c
@@ -262,6 +262,41 @@ fast_read_rgba_pixels( GLcontext *ctx,
}
+/**
+ * When we're using a low-precision color buffer (like 16-bit 5/6/5)
+ * we have to adjust our color values a bit to pass conformance.
+ * The problem is when a 5 or 6-bit color value is convert to an 8-bit
+ * value and then a floating point value, the floating point values don't
+ * increment uniformly as the 5 or 6-bit value is incremented.
+ *
+ * This function adjusts floating point values to compensate.
+ */
+static void
+adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
+{
+ const GLuint rShift = 8 - ctx->Visual.redBits;
+ const GLuint gShift = 8 - ctx->Visual.greenBits;
+ const GLuint bShift = 8 - ctx->Visual.blueBits;
+ const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits ) - 1);
+ const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
+ const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
+ GLuint i;
+ for (i = 0; i < n; i++) {
+ GLint r, g, b;
+ /* convert float back to ubyte */
+ CLAMPED_FLOAT_TO_UBYTE(r, rgba[i][RCOMP]);
+ CLAMPED_FLOAT_TO_UBYTE(g, rgba[i][GCOMP]);
+ CLAMPED_FLOAT_TO_UBYTE(b, rgba[i][BCOMP]);
+ /* using only the N most significant bits of the ubyte value, convert to
+ * float in [0,1].
+ */
+ rgba[i][RCOMP] = (GLfloat) (r >> rShift) * rScale;
+ rgba[i][GCOMP] = (GLfloat) (g >> gShift) * gScale;
+ rgba[i][BCOMP] = (GLfloat) (b >> bShift) * bScale;
+ }
+}
+
+
/*
* Read R, G, B, A, RGB, L, or LA pixels.
@@ -376,34 +411,18 @@ read_rgba_pixels( GLcontext *ctx,
_mesa_map_ci_to_rgba(ctx, width, index, rgba);
}
- /* pack the row of RGBA pixels into user's buffer */
-#if 0
- /* XXX may need to rejuvinate this code if we get conformance
- * falures on 16bpp displays (i.e. 5/6/5).
- */
- if (fb->Visual.redBits < CHAN_BITS ||
- fb->Visual.greenBits < CHAN_BITS ||
- fb->Visual.blueBits < CHAN_BITS) {
- /* Requantize the color values into floating point and go from
- * there. This fixes conformance failures with 5/6/5 color
- * buffers, for example.
- */
- GLfloat rgbaf[MAX_WIDTH][4];
- _mesa_chan_to_float_span(ctx, width,
- (CONST GLchan (*)[4]) rgba, rgbaf);
- _mesa_pack_rgba_span_float(ctx, width,
- (CONST GLfloat (*)[4]) rgbaf,
- format, type, dst, packing,
- ctx->_ImageTransferState);
- }
- else
-#endif
- {
- _mesa_pack_rgba_span_float(ctx, width, (CONST GLfloat (*)[4]) rgba,
- format, type, dst,
- packing, ctx->_ImageTransferState);
+ /* apply fudge factor for shallow color buffers */
+ if (fb->Visual.redBits < 8 ||
+ fb->Visual.greenBits < 8 ||
+ fb->Visual.blueBits < 8) {
+ adjust_colors(ctx, width, rgba);
}
+ /* pack the row of RGBA pixels into user's buffer */
+ _mesa_pack_rgba_span_float(ctx, width, (CONST GLfloat (*)[4]) rgba,
+ format, type, dst,
+ packing, ctx->_ImageTransferState);
+
dst += dstStride;
}
}