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Diffstat (limited to 'src/jpeg-6/jcsample.c')
| -rw-r--r-- | src/jpeg-6/jcsample.c | 519 |
1 files changed, 519 insertions, 0 deletions
diff --git a/src/jpeg-6/jcsample.c b/src/jpeg-6/jcsample.c new file mode 100644 index 0000000..bf0fb46 --- /dev/null +++ b/src/jpeg-6/jcsample.c @@ -0,0 +1,519 @@ +/* + * jcsample.c + * + * Copyright (C) 1991-1994, 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 downsampling routines. + * + * Downsampling input data is counted in "row groups". A row group + * is defined to be max_v_samp_factor pixel rows of each component, + * from which the downsampler produces v_samp_factor sample rows. + * A single row group is processed in each call to the downsampler module. + * + * The downsampler is responsible for edge-expansion of its output data + * to fill an integral number of DCT blocks horizontally. The source buffer + * may be modified if it is helpful for this purpose (the source buffer is + * allocated wide enough to correspond to the desired output width). + * The caller (the prep controller) is responsible for vertical padding. + * + * The downsampler may request "context rows" by setting need_context_rows + * during startup. In this case, the input arrays will contain at least + * one row group's worth of pixels above and below the passed-in data; + * the caller will create dummy rows at image top and bottom by replicating + * the first or last real pixel row. + * + * An excellent reference for image resampling is + * Digital Image Warping, George Wolberg, 1990. + * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. + * + * The downsampling algorithm used here is a simple average of the source + * pixels covered by the output pixel. The hi-falutin sampling literature + * refers to this as a "box filter". In general the characteristics of a box + * filter are not very good, but for the specific cases we normally use (1:1 + * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not + * nearly so bad. If you intend to use other sampling ratios, you'd be well + * advised to improve this code. + * + * A simple input-smoothing capability is provided. This is mainly intended + * for cleaning up color-dithered GIF input files (if you find it inadequate, + * we suggest using an external filtering program such as pnmconvol). When + * enabled, each input pixel P is replaced by a weighted sum of itself and its + * eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF, + * where SF = (smoothing_factor / 1024). + * Currently, smoothing is only supported for 2h2v sampling factors. + */ + +#define JPEG_INTERNALS +#include "jinclude.h" +#include "jpeglib.h" + + +/* Pointer to routine to downsample a single component */ +typedef JMETHOD(void, downsample1_ptr, + (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data)); + +/* Private subobject */ + +typedef struct { + struct jpeg_downsampler pub; /* public fields */ + + /* Downsampling method pointers, one per component */ + downsample1_ptr methods[MAX_COMPONENTS]; +} my_downsampler; + +typedef my_downsampler * my_downsample_ptr; + + +/* + * Initialize for a downsampling pass. + */ + +METHODDEF void +start_pass_downsample (j_compress_ptr cinfo) +{ + /* no work for now */ +} + + +/* + * Expand a component horizontally from width input_cols to width output_cols, + * by duplicating the rightmost samples. + */ + +LOCAL void +expand_right_edge (JSAMPARRAY image_data, int num_rows, + JDIMENSION input_cols, JDIMENSION output_cols) +{ + register JSAMPROW ptr; + register JSAMPLE pixval; + register int count; + int row; + int numcols = (int) (output_cols - input_cols); + + if (numcols > 0) { + for (row = 0; row < num_rows; row++) { + ptr = image_data[row] + input_cols; + pixval = ptr[-1]; /* don't need GETJSAMPLE() here */ + for (count = numcols; count > 0; count--) + *ptr++ = pixval; + } + } +} + + +/* + * Do downsampling for a whole row group (all components). + * + * In this version we simply downsample each component independently. + */ + +METHODDEF void +sep_downsample (j_compress_ptr cinfo, + JSAMPIMAGE input_buf, JDIMENSION in_row_index, + JSAMPIMAGE output_buf, JDIMENSION out_row_group_index) +{ + my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample; + int ci; + jpeg_component_info * compptr; + JSAMPARRAY in_ptr, out_ptr; + + for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; + ci++, compptr++) { + in_ptr = input_buf[ci] + in_row_index; + out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor); + (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr); + } +} + + +/* + * Downsample pixel values of a single component. + * One row group is processed per call. + * This version handles arbitrary integral sampling ratios, without smoothing. + * Note that this version is not actually used for customary sampling ratios. + */ + +METHODDEF void +int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v; + JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */ + JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; + JSAMPROW inptr, outptr; + INT32 outvalue; + + h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor; + v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor; + numpix = h_expand * v_expand; + numpix2 = numpix/2; + + /* Expand input data enough to let all the output samples be generated + * by the standard loop. Special-casing padded output would be more + * efficient. + */ + expand_right_edge(input_data, cinfo->max_v_samp_factor, + cinfo->image_width, output_cols * h_expand); + + inrow = 0; + for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { + outptr = output_data[outrow]; + for (outcol = 0, outcol_h = 0; outcol < output_cols; + outcol++, outcol_h += h_expand) { + outvalue = 0; + for (v = 0; v < v_expand; v++) { + inptr = input_data[inrow+v] + outcol_h; + for (h = 0; h < h_expand; h++) { + outvalue += (INT32) GETJSAMPLE(*inptr++); + } + } + *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix); + } + inrow += v_expand; + } +} + + +/* + * Downsample pixel values of a single component. + * This version handles the special case of a full-size component, + * without smoothing. + */ + +METHODDEF void +fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + /* Copy the data */ + jcopy_sample_rows(input_data, 0, output_data, 0, + cinfo->max_v_samp_factor, cinfo->image_width); + /* Edge-expand */ + expand_right_edge(output_data, cinfo->max_v_samp_factor, + cinfo->image_width, compptr->width_in_blocks * DCTSIZE); +} + + +/* + * Downsample pixel values of a single component. + * This version handles the common case of 2:1 horizontal and 1:1 vertical, + * without smoothing. + * + * A note about the "bias" calculations: when rounding fractional values to + * integer, we do not want to always round 0.5 up to the next integer. + * If we did that, we'd introduce a noticeable bias towards larger values. + * Instead, this code is arranged so that 0.5 will be rounded up or down at + * alternate pixel locations (a simple ordered dither pattern). + */ + +METHODDEF void +h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + int outrow; + JDIMENSION outcol; + JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; + register JSAMPROW inptr, outptr; + register int bias; + + /* Expand input data enough to let all the output samples be generated + * by the standard loop. Special-casing padded output would be more + * efficient. + */ + expand_right_edge(input_data, cinfo->max_v_samp_factor, + cinfo->image_width, output_cols * 2); + + for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { + outptr = output_data[outrow]; + inptr = input_data[outrow]; + bias = 0; /* bias = 0,1,0,1,... for successive samples */ + for (outcol = 0; outcol < output_cols; outcol++) { + *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1]) + + bias) >> 1); + bias ^= 1; /* 0=>1, 1=>0 */ + inptr += 2; + } + } +} + + +/* + * Downsample pixel values of a single component. + * This version handles the standard case of 2:1 horizontal and 2:1 vertical, + * without smoothing. + */ + +METHODDEF void +h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + int inrow, outrow; + JDIMENSION outcol; + JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; + register JSAMPROW inptr0, inptr1, outptr; + register int bias; + + /* Expand input data enough to let all the output samples be generated + * by the standard loop. Special-casing padded output would be more + * efficient. + */ + expand_right_edge(input_data, cinfo->max_v_samp_factor, + cinfo->image_width, output_cols * 2); + + inrow = 0; + for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { + outptr = output_data[outrow]; + inptr0 = input_data[inrow]; + inptr1 = input_data[inrow+1]; + bias = 1; /* bias = 1,2,1,2,... for successive samples */ + for (outcol = 0; outcol < output_cols; outcol++) { + *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + + GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]) + + bias) >> 2); + bias ^= 3; /* 1=>2, 2=>1 */ + inptr0 += 2; inptr1 += 2; + } + inrow += 2; + } +} + + +#ifdef INPUT_SMOOTHING_SUPPORTED + +/* + * Downsample pixel values of a single component. + * This version handles the standard case of 2:1 horizontal and 2:1 vertical, + * with smoothing. One row of context is required. + */ + +METHODDEF void +h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + int inrow, outrow; + JDIMENSION colctr; + JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; + register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr; + INT32 membersum, neighsum, memberscale, neighscale; + + /* Expand input data enough to let all the output samples be generated + * by the standard loop. Special-casing padded output would be more + * efficient. + */ + expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2, + cinfo->image_width, output_cols * 2); + + /* We don't bother to form the individual "smoothed" input pixel values; + * we can directly compute the output which is the average of the four + * smoothed values. Each of the four member pixels contributes a fraction + * (1-8*SF) to its own smoothed image and a fraction SF to each of the three + * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final + * output. The four corner-adjacent neighbor pixels contribute a fraction + * SF to just one smoothed pixel, or SF/4 to the final output; while the + * eight edge-adjacent neighbors contribute SF to each of two smoothed + * pixels, or SF/2 overall. In order to use integer arithmetic, these + * factors are scaled by 2^16 = 65536. + * Also recall that SF = smoothing_factor / 1024. + */ + + memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */ + neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */ + + inrow = 0; + for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { + outptr = output_data[outrow]; + inptr0 = input_data[inrow]; + inptr1 = input_data[inrow+1]; + above_ptr = input_data[inrow-1]; + below_ptr = input_data[inrow+2]; + + /* Special case for first column: pretend column -1 is same as column 0 */ + membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + + GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); + neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + + GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + + GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) + + GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]); + neighsum += neighsum; + neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) + + GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]); + membersum = membersum * memberscale + neighsum * neighscale; + *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); + inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2; + + for (colctr = output_cols - 2; colctr > 0; colctr--) { + /* sum of pixels directly mapped to this output element */ + membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + + GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); + /* sum of edge-neighbor pixels */ + neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + + GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + + GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) + + GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]); + /* The edge-neighbors count twice as much as corner-neighbors */ + neighsum += neighsum; + /* Add in the corner-neighbors */ + neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) + + GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]); + /* form final output scaled up by 2^16 */ + membersum = membersum * memberscale + neighsum * neighscale; + /* round, descale and output it */ + *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); + inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2; + } + + /* Special case for last column */ + membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + + GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); + neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + + GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + + GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) + + GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]); + neighsum += neighsum; + neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) + + GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]); + membersum = membersum * memberscale + neighsum * neighscale; + *outptr = (JSAMPLE) ((membersum + 32768) >> 16); + + inrow += 2; + } +} + + +/* + * Downsample pixel values of a single component. + * This version handles the special case of a full-size component, + * with smoothing. One row of context is required. + */ + +METHODDEF void +fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr, + JSAMPARRAY input_data, JSAMPARRAY output_data) +{ + int outrow; + JDIMENSION colctr; + JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; + register JSAMPROW inptr, above_ptr, below_ptr, outptr; + INT32 membersum, neighsum, memberscale, neighscale; + int colsum, lastcolsum, nextcolsum; + + /* Expand input data enough to let all the output samples be generated + * by the standard loop. Special-casing padded output would be more + * efficient. + */ + expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2, + cinfo->image_width, output_cols); + + /* Each of the eight neighbor pixels contributes a fraction SF to the + * smoothed pixel, while the main pixel contributes (1-8*SF). In order + * to use integer arithmetic, these factors are multiplied by 2^16 = 65536. + * Also recall that SF = smoothing_factor / 1024. + */ + + memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */ + neighscale = cinfo->smoothing_factor * 64; /* scaled SF */ + + for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { + outptr = output_data[outrow]; + inptr = input_data[outrow]; + above_ptr = input_data[outrow-1]; + below_ptr = input_data[outrow+1]; + + /* Special case for first column */ + colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) + + GETJSAMPLE(*inptr); + membersum = GETJSAMPLE(*inptr++); + nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) + + GETJSAMPLE(*inptr); + neighsum = colsum + (colsum - membersum) + nextcolsum; + membersum = membersum * memberscale + neighsum * neighscale; + *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); + lastcolsum = colsum; colsum = nextcolsum; + + for (colctr = output_cols - 2; colctr > 0; colctr--) { + membersum = GETJSAMPLE(*inptr++); + above_ptr++; below_ptr++; + nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) + + GETJSAMPLE(*inptr); + neighsum = lastcolsum + (colsum - membersum) + nextcolsum; + membersum = membersum * memberscale + neighsum * neighscale; + *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); + lastcolsum = colsum; colsum = nextcolsum; + } + + /* Special case for last column */ + membersum = GETJSAMPLE(*inptr); + neighsum = lastcolsum + (colsum - membersum) + colsum; + membersum = membersum * memberscale + neighsum * neighscale; + *outptr = (JSAMPLE) ((membersum + 32768) >> 16); + + } +} + +#endif /* INPUT_SMOOTHING_SUPPORTED */ + + +/* + * Module initialization routine for downsampling. + * Note that we must select a routine for each component. + */ + +GLOBAL void +jinit_downsampler (j_compress_ptr cinfo) +{ + my_downsample_ptr downsample; + int ci; + jpeg_component_info * compptr; + boolean smoothok = TRUE; + + downsample = (my_downsample_ptr) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + SIZEOF(my_downsampler)); + cinfo->downsample = (struct jpeg_downsampler *) downsample; + downsample->pub.start_pass = start_pass_downsample; + downsample->pub.downsample = sep_downsample; + downsample->pub.need_context_rows = FALSE; + + if (cinfo->CCIR601_sampling) + ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); + + /* Verify we can handle the sampling factors, and set up method pointers */ + for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; + ci++, compptr++) { + if (compptr->h_samp_factor == cinfo->max_h_samp_factor && + compptr->v_samp_factor == cinfo->max_v_samp_factor) { +#ifdef INPUT_SMOOTHING_SUPPORTED + if (cinfo->smoothing_factor) { + downsample->methods[ci] = fullsize_smooth_downsample; + downsample->pub.need_context_rows = TRUE; + } else +#endif + downsample->methods[ci] = fullsize_downsample; + } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor && + compptr->v_samp_factor == cinfo->max_v_samp_factor) { + smoothok = FALSE; + downsample->methods[ci] = h2v1_downsample; + } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor && + compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) { +#ifdef INPUT_SMOOTHING_SUPPORTED + if (cinfo->smoothing_factor) { + downsample->methods[ci] = h2v2_smooth_downsample; + downsample->pub.need_context_rows = TRUE; + } else +#endif + downsample->methods[ci] = h2v2_downsample; + } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 && + (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) { + smoothok = FALSE; + downsample->methods[ci] = int_downsample; + } else + ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); + } + +#ifdef INPUT_SMOOTHING_SUPPORTED + if (cinfo->smoothing_factor && !smoothok) + TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL); +#endif +} |