- else
- {
- png_byte shift, sig_bit;
-
- if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
- {
- sig_bit = png_ptr->sig_bit.red;
-
- if (png_ptr->sig_bit.green > sig_bit)
- sig_bit = png_ptr->sig_bit.green;
-
- if (png_ptr->sig_bit.blue > sig_bit)
- sig_bit = png_ptr->sig_bit.blue;
- }
- else
- sig_bit = png_ptr->sig_bit.gray;
-
- /* 16-bit gamma code uses this equation:
- *
- * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
- *
- * Where 'iv' is the input color value and 'ov' is the output value -
- * pow(iv, gamma).
- *
- * Thus the gamma table consists of up to 256 256 entry tables. The table
- * is selected by the (8-gamma_shift) most significant of the low 8 bits of
- * the color value then indexed by the upper 8 bits:
- *
- * table[low bits][high 8 bits]
- *
- * So the table 'n' corresponds to all those 'iv' of:
- *
- * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
- *
- */
- if (sig_bit > 0 && sig_bit < 16U)
- shift = (png_byte)(16U - sig_bit); /* shift == insignificant bits */
-
- else
- shift = 0; /* keep all 16 bits */
-
- if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
- {
- /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
- * the significant bits in the *input* when the output will
- * eventually be 8 bits. By default it is 11.
- */
- if (shift < (16U - PNG_MAX_GAMMA_8))
- shift = (16U - PNG_MAX_GAMMA_8);
- }
-
- if (shift > 8U)
- shift = 8U; /* Guarantees at least one table! */
-
- png_ptr->gamma_shift = shift;
-
- /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
- * PNG_COMPOSE). This effectively smashed the background calculation for
- * 16-bit output because the 8-bit table assumes the result will be reduced
- * to 8 bits.
- */
- if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
- png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
- png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
- png_ptr->screen_gamma) : PNG_FP_1);
-
- else
- png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
- png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
- png_ptr->screen_gamma) : PNG_FP_1);
+ else
+ {
+ png_byte shift, sig_bit;
+
+ if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
+ {
+ sig_bit = png_ptr->sig_bit.red;
+
+ if (png_ptr->sig_bit.green > sig_bit)
+ sig_bit = png_ptr->sig_bit.green;
+
+ if (png_ptr->sig_bit.blue > sig_bit)
+ sig_bit = png_ptr->sig_bit.blue;
+ }
+ else
+ sig_bit = png_ptr->sig_bit.gray;
+
+ /* 16-bit gamma code uses this equation:
+ *
+ * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
+ *
+ * Where 'iv' is the input color value and 'ov' is the output value -
+ * pow(iv, gamma).
+ *
+ * Thus the gamma table consists of up to 256 256-entry tables. The table
+ * is selected by the (8-gamma_shift) most significant of the low 8 bits
+ * of the color value then indexed by the upper 8 bits:
+ *
+ * table[low bits][high 8 bits]
+ *
+ * So the table 'n' corresponds to all those 'iv' of:
+ *
+ * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
+ *
+ */
+ if (sig_bit > 0 && sig_bit < 16U)
+ /* shift == insignificant bits */
+ shift = (png_byte)((16U - sig_bit) & 0xff);
+
+ else
+ shift = 0; /* keep all 16 bits */
+
+ if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
+ {
+ /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
+ * the significant bits in the *input* when the output will
+ * eventually be 8 bits. By default it is 11.
+ */
+ if (shift < (16U - PNG_MAX_GAMMA_8))
+ shift = (16U - PNG_MAX_GAMMA_8);
+ }
+
+ if (shift > 8U)
+ shift = 8U; /* Guarantees at least one table! */
+
+ png_ptr->gamma_shift = shift;
+
+ /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
+ * PNG_COMPOSE). This effectively smashed the background calculation for
+ * 16-bit output because the 8-bit table assumes the result will be
+ * reduced to 8 bits.
+ */
+ if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
+ png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
+ png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
+ png_ptr->screen_gamma) : PNG_FP_1);
+
+ else
+ png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
+ png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
+ png_ptr->screen_gamma) : PNG_FP_1);