63 uint16_t
lut[4][256 * 256];
83 #define OFFSET(x) offsetof(LutContext, x) 84 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM 106 for (i = 0; i < 4; i++) {
113 #define YUV_FORMATS \ 114 AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV420P, \ 115 AV_PIX_FMT_YUV411P, AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV440P, \ 116 AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA444P, \ 117 AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ420P, \ 118 AV_PIX_FMT_YUVJ440P, \ 119 AV_PIX_FMT_YUV444P9LE, AV_PIX_FMT_YUV422P9LE, AV_PIX_FMT_YUV420P9LE, \ 120 AV_PIX_FMT_YUV444P10LE, AV_PIX_FMT_YUV422P10LE, AV_PIX_FMT_YUV420P10LE, AV_PIX_FMT_YUV440P10LE, \ 121 AV_PIX_FMT_YUV444P12LE, AV_PIX_FMT_YUV422P12LE, AV_PIX_FMT_YUV420P12LE, AV_PIX_FMT_YUV440P12LE, \ 122 AV_PIX_FMT_YUV444P14LE, AV_PIX_FMT_YUV422P14LE, AV_PIX_FMT_YUV420P14LE, \ 123 AV_PIX_FMT_YUV444P16LE, AV_PIX_FMT_YUV422P16LE, AV_PIX_FMT_YUV420P16LE, \ 124 AV_PIX_FMT_YUVA444P16LE, AV_PIX_FMT_YUVA422P16LE, AV_PIX_FMT_YUVA420P16LE 126 #define RGB_FORMATS \ 127 AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA, \ 128 AV_PIX_FMT_ABGR, AV_PIX_FMT_BGRA, \ 129 AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24, \ 130 AV_PIX_FMT_RGB48LE, AV_PIX_FMT_RGBA64LE, \ 131 AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP, \ 132 AV_PIX_FMT_GBRP9LE, AV_PIX_FMT_GBRP10LE, \ 133 AV_PIX_FMT_GBRAP10LE, \ 134 AV_PIX_FMT_GBRP12LE, AV_PIX_FMT_GBRP14LE, \ 135 AV_PIX_FMT_GBRP16LE, AV_PIX_FMT_GBRAP12LE, \ 138 #define GRAY_FORMATS \ 139 AV_PIX_FMT_GRAY8, AV_PIX_FMT_GRAY9LE, AV_PIX_FMT_GRAY10LE, \ 140 AV_PIX_FMT_GRAY12LE, AV_PIX_FMT_GRAY14LE, AV_PIX_FMT_GRAY16LE 168 return av_clip(val, minval, maxval);
182 return pow((val-minval)/(maxval-minval), gamma) * (maxval-minval)+minval;
194 double level = (val - minval) / (maxval - minval);
195 level = level < 0.018 ? 4.5 * level
196 : 1.099 * pow(level, 1.0 / gamma) - 0.099;
197 return level * (maxval - minval) + minval;
200 static double (*
const funcs1[])(
void *, double) = {
266 min[
Y] = 16 * (1 << (desc->
comp[0].
depth - 8));
267 min[
U] = 16 * (1 << (desc->
comp[1].
depth - 8));
268 min[
V] = 16 * (1 << (desc->
comp[2].
depth - 8));
270 max[
Y] = 235 * (1 << (desc->
comp[0].
depth - 8));
271 max[
U] = 240 * (1 << (desc->
comp[1].
depth - 8));
272 max[
V] = 240 * (1 << (desc->
comp[2].
depth - 8));
277 min[0] = min[1] = min[2] = min[3] = 0;
278 max[0] = max[1] = max[2] = max[3] = 65535;
281 min[0] = min[1] = min[2] = min[3] = 0;
282 max[0] = max[1] = max[2] = max[3] = 255 * (1 << (desc->
comp[0].
depth - 8));
309 "Error when parsing the expression '%s' for the component %d and color %d.\n",
323 min[color], max[color]);
328 "Error when evaluating the expression '%s' for the value %d for the component %d.\n",
348 #define LOAD_PACKED_COMMON\ 349 LutContext *s = ctx->priv;\ 350 const struct thread_data *td = arg;\ 353 const int w = td->w;\ 354 const int h = td->h;\ 355 AVFrame *in = td->in;\ 356 AVFrame *out = td->out;\ 357 const uint16_t (*tab)[256*256] = (const uint16_t (*)[256*256])s->lut;\ 358 const int step = s->step;\ 360 const int slice_start = (h * jobnr ) / nb_jobs;\ 361 const int slice_end = (h * (jobnr+1)) / nb_jobs;\ 368 uint16_t *inrow, *outrow, *inrow0, *outrow0;
369 const int in_linesize =
in->linesize[0] / 2;
370 const int out_linesize =
out->linesize[0] / 2;
371 inrow0 = (uint16_t *)
in ->
data[0];
372 outrow0 = (uint16_t *)
out->data[0];
375 inrow = inrow0 +
i * in_linesize;
376 outrow = outrow0 +
i * out_linesize;
377 for (j = 0; j <
w; j++) {
386 case 4: outrow[3] =
tab[3][inrow[3]];
387 case 3: outrow[2] =
tab[2][inrow[2]];
388 case 2: outrow[1] =
tab[1][inrow[1]];
389 default: outrow[0] =
tab[0][inrow[0]];
405 uint8_t *inrow, *outrow, *inrow0, *outrow0;
406 const int in_linesize =
in->linesize[0];
407 const int out_linesize =
out->linesize[0];
408 inrow0 =
in ->data[0];
409 outrow0 =
out->data[0];
412 inrow = inrow0 +
i * in_linesize;
413 outrow = outrow0 +
i * out_linesize;
414 for (j = 0; j <
w; j++) {
416 case 4: outrow[3] =
tab[3][inrow[3]];
417 case 3: outrow[2] =
tab[2][inrow[2]];
418 case 2: outrow[1] =
tab[1][inrow[1]];
419 default: outrow[0] =
tab[0][inrow[0]];
429 #define LOAD_PLANAR_COMMON\ 430 LutContext *s = ctx->priv;\ 431 const struct thread_data *td = arg;\ 433 AVFrame *in = td->in;\ 434 AVFrame *out = td->out;\ 436 #define PLANAR_COMMON\ 437 int vsub = plane == 1 || plane == 2 ? s->vsub : 0;\ 438 int hsub = plane == 1 || plane == 2 ? s->hsub : 0;\ 439 int h = AV_CEIL_RSHIFT(td->h, vsub);\ 440 int w = AV_CEIL_RSHIFT(td->w, hsub);\ 441 const uint16_t *tab = s->lut[plane];\ 443 const int slice_start = (h * jobnr ) / nb_jobs;\ 444 const int slice_end = (h * (jobnr+1)) / nb_jobs;\ 451 uint16_t *inrow, *outrow;
456 const int in_linesize =
in->linesize[
plane] / 2;
457 const int out_linesize =
out->linesize[
plane] / 2;
459 inrow = (uint16_t *)
in ->
data[
plane] + slice_start * in_linesize;
460 outrow = (uint16_t *)
out->data[
plane] + slice_start * out_linesize;
463 for (j = 0; j <
w; j++) {
467 outrow[j] =
tab[inrow[j]];
470 inrow += in_linesize;
471 outrow += out_linesize;
488 const int in_linesize =
in->linesize[
plane];
489 const int out_linesize =
out->linesize[
plane];
491 inrow =
in ->data[
plane] + slice_start * in_linesize;
492 outrow =
out->data[
plane] + slice_start * out_linesize;
495 for (j = 0; j <
w; j++)
496 outrow[j] =
tab[inrow[j]];
497 inrow += in_linesize;
498 outrow += out_linesize;
505 #define PACKED_THREAD_DATA\ 506 struct thread_data td = {\ 513 #define PLANAR_THREAD_DATA\ 514 struct thread_data td = {\ 584 #define DEFINE_LUT_FILTER(name_, description_) \ 585 AVFilter ff_vf_##name_ = { \ 587 .description = NULL_IF_CONFIG_SMALL(description_), \ 588 .priv_size = sizeof(LutContext), \ 589 .priv_class = &name_ ## _class, \ 590 .init = name_##_init, \ 592 .query_formats = query_formats, \ 594 .outputs = outputs, \ 595 .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS, \ 598 #if CONFIG_LUT_FILTER 600 #define lut_options options 611 #if CONFIG_LUTYUV_FILTER 613 #define lutyuv_options options 625 DEFINE_LUT_FILTER(lutyuv,
"Compute and apply a lookup table to the YUV input video.");
628 #if CONFIG_LUTRGB_FILTER 630 #define lutrgb_options options 642 DEFINE_LUT_FILTER(lutrgb,
"Compute and apply a lookup table to the RGB input video.");
645 #if CONFIG_NEGATE_FILTER 647 static const AVOption negate_options[] = {
661 for (i = 0; i < 4; i++) {
const char const char void * val
planar YUV 4:4:0,20bpp, (1 Cr & Cb sample per 1x2 Y samples), little-endian
planar YUV 4:2:0,21bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
const AVPixFmtDescriptor * av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
This structure describes decoded (raw) audio or video data.
ptrdiff_t const GLvoid * data
planar YUV 4:2:2,28bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
Main libavfilter public API header.
int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc)
Return the number of bits per pixel used by the pixel format described by pixdesc.
int h
agreed upon image height
static int lut_planar_16bits(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
static const AVOption options[]
planar YUV 4:4:4 40bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)
static const char *const funcs1_names[]
int av_expr_parse(AVExpr **expr, const char *s, const char *const *const_names, const char *const *func1_names, double(*const *funcs1)(void *, double), const char *const *func2_names, double(*const *funcs2)(void *, double, double), int log_offset, void *log_ctx)
Parse an expression.
AVFrame * ff_get_video_buffer(AVFilterLink *link, int w, int h)
Request a picture buffer with a specific set of permissions.
planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
uint8_t log2_chroma_w
Amount to shift the luma width right to find the chroma width.
static enum AVPixelFormat yuv_pix_fmts[]
static double compute_gammaval709(void *opaque, double gamma)
Compute ITU Rec.709 gamma correction of value val.
Macro definitions for various function/variable attributes.
const char * name
Pad name.
planar YUV 4:2:0 22.5bpp, (1 Cr & Cb sample per 2x2 Y & A samples), little-endian ...
static const char *const var_names[]
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)
AVComponentDescriptor comp[4]
Parameters that describe how pixels are packed.
packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as lit...
static const uint32_t color[16+AV_CLASS_CATEGORY_NB]
planar YUV 4:4:4,36bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
static double(*const funcs1[])(void *, double)
planar YUV 4:2:0 40bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)
#define PACKED_THREAD_DATA
#define LOAD_PACKED_COMMON
A filter pad used for either input or output.
planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
A link between two filters.
static enum AVPixelFormat all_pix_fmts[]
planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)
#define i(width, name, range_min, range_max)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
uint8_t log2_chroma_h
Amount to shift the luma height right to find the chroma height.
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
static int lut_planar_8bits(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
void * priv
private data for use by the filter
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
uint16_t lut[4][256 *256]
lookup table for each component
planar YUV 4:4:4 36bpp, (1 Cr & Cb sample per 1x1 Y & A samples), little-endian
static int lut_packed_8bits(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
int w
agreed upon image width
uint64_t flags
Combination of AV_PIX_FMT_FLAG_...
double var_values[VAR_VARS_NB]
uint8_t nb_components
The number of components each pixel has, (1-4)
int ff_filter_get_nb_threads(AVFilterContext *ctx)
Get number of threads for current filter instance.
#define LOAD_PLANAR_COMMON
planar YUV 4:2:0,18bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
#define PLANAR_THREAD_DATA
planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
int format
agreed upon media format
#define FF_ARRAY_ELEMS(a)
int ff_fill_rgba_map(uint8_t *rgba_map, enum AVPixelFormat pix_fmt)
static void comp(unsigned char *dst, ptrdiff_t dst_stride, unsigned char *src, ptrdiff_t src_stride, int add)
char * av_strdup(const char *s)
Duplicate a string.
void av_expr_free(AVExpr *e)
Free a parsed expression previously created with av_expr_parse().
int av_frame_is_writable(AVFrame *frame)
Check if the frame data is writable.
static const AVFilterPad outputs[]
planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)
Descriptor that unambiguously describes how the bits of a pixel are stored in the up to 4 data planes...
planar YUV 4:4:0,24bpp, (1 Cr & Cb sample per 1x2 Y samples), little-endian
static int query_formats(AVFilterContext *ctx)
uint8_t pi<< 24) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_U8, uint8_t,(*(const uint8_t *) pi-0x80)*(1.0f/(1<< 7))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_U8, uint8_t,(*(const uint8_t *) pi-0x80)*(1.0/(1<< 7))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_S16, int16_t,(*(const int16_t *) pi >> 8)+0x80) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_S16, int16_t,*(const int16_t *) pi *(1.0f/(1<< 15))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_S16, int16_t,*(const int16_t *) pi *(1.0/(1<< 15))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_S32, int32_t,(*(const int32_t *) pi >> 24)+0x80) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_S32, int32_t,*(const int32_t *) pi *(1.0f/(1U<< 31))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_S32, int32_t,*(const int32_t *) pi *(1.0/(1U<< 31))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_FLT, float, av_clip_uint8(lrintf(*(const float *) pi *(1<< 7))+0x80)) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S16, int16_t, AV_SAMPLE_FMT_FLT, float, av_clip_int16(lrintf(*(const float *) pi *(1<< 15)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S32, int32_t, AV_SAMPLE_FMT_FLT, float, av_clipl_int32(llrintf(*(const float *) pi *(1U<< 31)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_DBL, double, av_clip_uint8(lrint(*(const double *) pi *(1<< 7))+0x80)) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S16, int16_t, AV_SAMPLE_FMT_DBL, double, av_clip_int16(lrint(*(const double *) pi *(1<< 15)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S32, int32_t, AV_SAMPLE_FMT_DBL, double, av_clipl_int32(llrint(*(const double *) pi *(1U<< 31))))#define SET_CONV_FUNC_GROUP(ofmt, ifmt) static void set_generic_function(AudioConvert *ac){}void ff_audio_convert_free(AudioConvert **ac){if(!*ac) return;ff_dither_free(&(*ac) ->dc);av_freep(ac);}AudioConvert *ff_audio_convert_alloc(AVAudioResampleContext *avr, enum AVSampleFormat out_fmt, enum AVSampleFormat in_fmt, int channels, int sample_rate, int apply_map){AudioConvert *ac;int in_planar, out_planar;ac=av_mallocz(sizeof(*ac));if(!ac) return NULL;ac->avr=avr;ac->out_fmt=out_fmt;ac->in_fmt=in_fmt;ac->channels=channels;ac->apply_map=apply_map;if(avr->dither_method!=AV_RESAMPLE_DITHER_NONE &&av_get_packed_sample_fmt(out_fmt)==AV_SAMPLE_FMT_S16 &&av_get_bytes_per_sample(in_fmt) > 2){ac->dc=ff_dither_alloc(avr, out_fmt, in_fmt, channels, sample_rate, apply_map);if(!ac->dc){av_free(ac);return NULL;}return ac;}in_planar=ff_sample_fmt_is_planar(in_fmt, channels);out_planar=ff_sample_fmt_is_planar(out_fmt, channels);if(in_planar==out_planar){ac->func_type=CONV_FUNC_TYPE_FLAT;ac->planes=in_planar?ac->channels:1;}else if(in_planar) ac->func_type=CONV_FUNC_TYPE_INTERLEAVE;else ac->func_type=CONV_FUNC_TYPE_DEINTERLEAVE;set_generic_function(ac);if(ARCH_AARCH64) ff_audio_convert_init_aarch64(ac);if(ARCH_ARM) ff_audio_convert_init_arm(ac);if(ARCH_X86) ff_audio_convert_init_x86(ac);return ac;}int ff_audio_convert(AudioConvert *ac, AudioData *out, AudioData *in){int use_generic=1;int len=in->nb_samples;int p;if(ac->dc){av_log(ac->avr, AV_LOG_TRACE,"%d samples - audio_convert: %s to %s (dithered)\n", len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt));return ff_convert_dither(ac-> in
planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples)
planar YUV 4:2:2 48bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)
Describe the class of an AVClass context structure.
planar YUV 4:4:4 64bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)
AVFilterLink ** outputs
array of pointers to output links
static enum AVPixelFormat pix_fmts[]
planar YUV 4:2:2 30bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)
AVFilterInternal * internal
An opaque struct for libavfilter internal use.
#define DEFINE_LUT_FILTER(name_, description_)
planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
The exact code depends on how similar the blocks are and how related they are to the and needs to apply these operations to the correct inlink or outlink if there are several Macros are available to factor that when no extra processing is inlink
static enum AVPixelFormat rgb_pix_fmts[]
static int lut_packed_16bits(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
static const AVFilterPad inputs[]
static int config_props(AVFilterLink *inlink)
planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
planar YUV 4:2:2,24bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
static av_cold void uninit(AVFilterContext *ctx)
common internal and external API header
static double clip(void *opaque, double val)
Clip value val in the minval - maxval range.
planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)
avfilter_execute_func * execute
planar YUV 4:2:0 25bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)
static int slice_end(AVCodecContext *avctx, AVFrame *pict)
Handle slice ends.
planar YUV 4:4:4,42bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
double av_expr_eval(AVExpr *e, const double *const_values, void *opaque)
Evaluate a previously parsed expression.
AVFilterContext * dst
dest filter
#define AVFILTER_DEFINE_CLASS(fname)
static const struct twinvq_data tab
static double compute_gammaval(void *opaque, double gamma)
Compute gamma correction for value val, assuming the minval-maxval range, val is clipped to a value c...
planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)
planar YUV 4:2:2 27bpp, (1 Cr & Cb sample per 2x1 Y & A samples), little-endian
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
int depth
Number of bits in the component.
AVPixelFormat
Pixel format.
#define AV_PIX_FMT_FLAG_PLANAR
At least one pixel component is not in the first data plane.
int av_frame_copy_props(AVFrame *dst, const AVFrame *src)
Copy only "metadata" fields from src to dst.
packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is st...
simple arithmetic expression evaluator