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change the LUT function for the contrast. Fixes the buggy behaviour as
2006-02-24 Simon Budig <simon@gimp.org> * app/base/lut-funcs.c: change the LUT function for the contrast. Fixes the buggy behaviour as described in bug #319872 and bug #332068 and makes the behaviour consistent with the standard contrast formula. However, I am leaving the bug open to discuss further improvements. Untabbified.
This commit is contained in:
Simon Budig
Simon Budig
parent
3343baa84c
commit
78c41aa68f
10
ChangeLog
10
ChangeLog
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@ -1,3 +1,13 @@
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2006-02-24 Simon Budig <simon@gimp.org>
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* app/base/lut-funcs.c: change the LUT function for the contrast.
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Fixes the buggy behaviour as described in bug #319872 and
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bug #332068 and makes the behaviour consistent with the standard
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contrast formula. However, I am leaving the bug open to discuss
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further improvements.
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Untabbified.
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2006-02-23 Sven Neumann <sven@gimp.org>
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* libgimpbase/gimpwire.[ch]: added utility functions to send
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@ -39,12 +39,11 @@ typedef struct B_C_struct
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static gfloat
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brightness_contrast_lut_func (B_C_struct *data,
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gint nchannels,
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gint channel,
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gfloat value)
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gint nchannels,
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gint channel,
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gfloat value)
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{
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gfloat nvalue;
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gdouble power;
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gdouble slant;
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/* return the original value for the alpha channel */
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if ((nchannels == 2 || nchannels == 4) && channel == nchannels -1)
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@ -56,50 +55,16 @@ brightness_contrast_lut_func (B_C_struct *data,
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else
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value = value + ((1.0 - value) * data->brightness);
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/* apply contrast */
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if (data->contrast < 0.0)
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{
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if (value > 0.5)
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nvalue = 1.0 - value;
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else
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nvalue = value;
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if (nvalue < 0.0)
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nvalue = 0.0;
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nvalue = 0.5 * pow (nvalue * 2.0 , (double) (1.0 + data->contrast));
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if (value > 0.5)
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value = 1.0 - nvalue;
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else
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value = nvalue;
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}
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else
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{
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if (value > 0.5)
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nvalue = 1.0 - value;
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else
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nvalue = value;
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if (nvalue < 0.0)
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nvalue = 0.0;
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power = (data->contrast == 1.0) ? 127 : 1.0 / (1.0 - data->contrast);
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nvalue = 0.5 * pow (2.0 * nvalue, power);
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if (value > 0.5)
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value = 1.0 - nvalue;
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else
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value = nvalue;
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}
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slant = tan ((data->contrast + 1) * G_PI_4);
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value = (value - 0.5) * slant + 0.5;
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return value;
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}
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GimpLut *
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brightness_contrast_lut_new (gdouble brightness,
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gdouble contrast,
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gint n_channels)
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gdouble contrast,
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gint n_channels)
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{
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GimpLut *lut;
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@ -112,9 +77,9 @@ brightness_contrast_lut_new (gdouble brightness,
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void
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brightness_contrast_lut_setup (GimpLut *lut,
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gdouble brightness,
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gdouble contrast,
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gint n_channels)
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gdouble brightness,
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gdouble contrast,
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gint n_channels)
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{
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B_C_struct data;
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@ -124,16 +89,16 @@ brightness_contrast_lut_setup (GimpLut *lut,
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data.contrast = contrast;
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gimp_lut_setup (lut, (GimpLutFunc) brightness_contrast_lut_func,
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(gpointer) &data, n_channels);
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(gpointer) &data, n_channels);
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}
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/* ---------------- invert ------------------ */
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static gfloat
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invert_lut_func (gpointer unused,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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/* don't invert the alpha channel */
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if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
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@ -156,21 +121,21 @@ invert_lut_new (gint n_channels)
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void
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invert_lut_setup (GimpLut *lut,
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gint n_channels)
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gint n_channels)
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{
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g_return_if_fail (lut != NULL);
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gimp_lut_setup_exact (lut, (GimpLutFunc) invert_lut_func,
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NULL , n_channels);
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NULL , n_channels);
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}
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/* ---------------- add (or subract)------------------ */
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static gfloat
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add_lut_func (gdouble *amount,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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/* don't change the alpha channel */
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if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
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@ -181,7 +146,7 @@ add_lut_func (gdouble *amount,
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GimpLut *
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add_lut_new (gdouble amount,
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gint n_channels)
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gint n_channels)
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{
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GimpLut *lut;
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@ -194,22 +159,22 @@ add_lut_new (gdouble amount,
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void
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add_lut_setup (GimpLut *lut,
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gdouble amount,
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gint n_channels)
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gdouble amount,
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gint n_channels)
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{
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g_return_if_fail (lut != NULL);
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gimp_lut_setup (lut, (GimpLutFunc) add_lut_func,
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(gpointer) &amount, n_channels);
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(gpointer) &amount, n_channels);
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}
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/* ---------------- intersect (MIN (pixel, value)) ------------------ */
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static gfloat
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intersect_lut_func (gdouble *min,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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/* don't change the alpha channel */
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if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
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@ -220,7 +185,7 @@ intersect_lut_func (gdouble *min,
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GimpLut *
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intersect_lut_new (gdouble value,
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gint n_channels)
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gint n_channels)
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{
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GimpLut *lut;
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@ -233,22 +198,22 @@ intersect_lut_new (gdouble value,
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void
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intersect_lut_setup (GimpLut *lut,
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gdouble value,
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gint n_channels)
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gdouble value,
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gint n_channels)
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{
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g_return_if_fail (lut != NULL);
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gimp_lut_setup_exact (lut, (GimpLutFunc) intersect_lut_func,
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(gpointer) &value , n_channels);
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(gpointer) &value , n_channels);
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}
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/* ---------------- Threshold ------------------ */
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static gfloat
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threshold_lut_func (gdouble *min,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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/* don't change the alpha channel */
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if ((n_channels == 2 || n_channels == 4) && channel == n_channels -1)
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@ -262,7 +227,7 @@ threshold_lut_func (gdouble *min,
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GimpLut *
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threshold_lut_new (gdouble value,
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gint n_channels)
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gint n_channels)
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{
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GimpLut *lut;
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@ -275,22 +240,22 @@ threshold_lut_new (gdouble value,
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void
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threshold_lut_setup (GimpLut *lut,
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gdouble value,
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gint n_channels)
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gdouble value,
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gint n_channels)
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{
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g_return_if_fail (lut != NULL);
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gimp_lut_setup_exact (lut, (GimpLutFunc) threshold_lut_func,
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(gpointer) &value , n_channels);
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(gpointer) &value , n_channels);
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}
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/* --------------- posterize ---------------- */
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static gfloat
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posterize_lut_func (gint *ilevels,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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gint levels;
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@ -310,7 +275,7 @@ posterize_lut_func (gint *ilevels,
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GimpLut *
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posterize_lut_new (gint levels,
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gint n_channels)
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gint n_channels)
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{
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GimpLut *lut;
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@ -323,13 +288,13 @@ posterize_lut_new (gint levels,
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void
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posterize_lut_setup (GimpLut *lut,
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gint levels,
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gint n_channels)
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gint levels,
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gint n_channels)
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{
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g_return_if_fail (lut != NULL);
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gimp_lut_setup_exact (lut, (GimpLutFunc) posterize_lut_func,
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(gpointer) &levels, n_channels);
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(gpointer) &levels, n_channels);
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}
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/* --------------- equalize ------------- */
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@ -342,9 +307,9 @@ typedef struct
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static gfloat
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equalize_lut_func (hist_lut_struct *hlut,
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gint n_channels,
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gint channel,
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gfloat value)
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gint n_channels,
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gint channel,
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gfloat value)
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{
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gint i = 0;
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gint j;
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@ -359,7 +324,7 @@ equalize_lut_func (hist_lut_struct *hlut,
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GimpLut *
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eq_histogram_lut_new (GimpHistogram *histogram,
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gint n_channels)
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gint n_channels)
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{
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GimpLut *lut;
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@ -374,8 +339,8 @@ eq_histogram_lut_new (GimpHistogram *histogram,
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void
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eq_histogram_lut_setup (GimpLut *lut,
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GimpHistogram *hist,
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gint n_channels)
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GimpHistogram *hist,
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gint n_channels)
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{
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gint i, k, j;
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hist_lut_struct hlut;
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@ -400,28 +365,28 @@ eq_histogram_lut_setup (GimpLut *lut,
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/* Find intermediate points */
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j = 0;
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sum = (gimp_histogram_get_channel (hist, k, 0) +
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gimp_histogram_get_channel (hist, k, 1));
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gimp_histogram_get_channel (hist, k, 1));
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for (i = 1; i < 256; i++)
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{
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desired = i * pixels_per_value;
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{
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desired = i * pixels_per_value;
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while (sum <= desired)
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{
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j++;
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sum += gimp_histogram_get_channel (hist, k, j + 1);
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}
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while (sum <= desired)
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{
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j++;
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sum += gimp_histogram_get_channel (hist, k, j + 1);
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}
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/* Nearest sum */
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dif = sum - gimp_histogram_get_channel (hist, k, j);
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/* Nearest sum */
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dif = sum - gimp_histogram_get_channel (hist, k, j);
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if ((sum - desired) > (dif / 2.0))
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hlut.part[k][i] = j;
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else
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hlut.part[k][i] = j + 1;
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}
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if ((sum - desired) > (dif / 2.0))
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hlut.part[k][i] = j;
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else
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hlut.part[k][i] = j + 1;
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}
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}
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gimp_lut_setup (lut, (GimpLutFunc) equalize_lut_func,
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(gpointer) &hlut, n_channels);
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(gpointer) &hlut, n_channels);
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}
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