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+/*
+ * jdsample.c
+ *
+ * Copyright (C) 1991-1996, 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 upsampling routines.
+ *
+ * Upsampling input data is counted in "row groups". A row group
+ * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
+ * sample rows of each component. Upsampling will normally produce
+ * max_v_samp_factor pixel rows from each row group (but this could vary
+ * if the upsampler is applying a scale factor of its own).
+ *
+ * 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.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+
+
+/* Pointer to routine to upsample a single component */
+typedef JMETHOD(void, upsample1_ptr,
+ (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
+
+/* Private subobject */
+
+typedef struct {
+ struct jpeg_upsampler pub; /* public fields */
+
+ /* Color conversion buffer. When using separate upsampling and color
+ * conversion steps, this buffer holds one upsampled row group until it
+ * has been color converted and output.
+ * Note: we do not allocate any storage for component(s) which are full-size,
+ * ie do not need rescaling. The corresponding entry of color_buf[] is
+ * simply set to point to the input data array, thereby avoiding copying.
+ */
+ JSAMPARRAY color_buf[MAX_COMPONENTS];
+
+ /* Per-component upsampling method pointers */
+ upsample1_ptr methods[MAX_COMPONENTS];
+
+ int next_row_out; /* counts rows emitted from color_buf */
+ JDIMENSION rows_to_go; /* counts rows remaining in image */
+
+ /* Height of an input row group for each component. */
+ int rowgroup_height[MAX_COMPONENTS];
+
+ /* These arrays save pixel expansion factors so that int_expand need not
+ * recompute them each time. They are unused for other upsampling methods.
+ */
+ UINT8 h_expand[MAX_COMPONENTS];
+ UINT8 v_expand[MAX_COMPONENTS];
+} my_upsampler;
+
+typedef my_upsampler * my_upsample_ptr;
+
+
+/*
+ * Initialize for an upsampling pass.
+ */
+
+METHODDEF(void)
+start_pass_upsample (j_decompress_ptr cinfo)
+{
+ my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
+
+ /* Mark the conversion buffer empty */
+ upsample->next_row_out = cinfo->max_v_samp_factor;
+ /* Initialize total-height counter for detecting bottom of image */
+ upsample->rows_to_go = cinfo->output_height;
+}
+
+
+/*
+ * Control routine to do upsampling (and color conversion).
+ *
+ * In this version we upsample each component independently.
+ * We upsample one row group into the conversion buffer, then apply
+ * color conversion a row at a time.
+ */
+
+METHODDEF(void)
+sep_upsample (j_decompress_ptr cinfo,
+ JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
+ JDIMENSION in_row_groups_avail,
+ JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
+ JDIMENSION out_rows_avail)
+{
+ my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
+ int ci;
+ jpeg_component_info * compptr;
+ JDIMENSION num_rows;
+
+ /* Fill the conversion buffer, if it's empty */
+ if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ /* Invoke per-component upsample method. Notice we pass a POINTER
+ * to color_buf[ci], so that fullsize_upsample can change it.
+ */
+ (*upsample->methods[ci]) (cinfo, compptr,
+ input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
+ upsample->color_buf + ci);
+ }
+ upsample->next_row_out = 0;
+ }
+
+ /* Color-convert and emit rows */
+
+ /* How many we have in the buffer: */
+ num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
+ /* Not more than the distance to the end of the image. Need this test
+ * in case the image height is not a multiple of max_v_samp_factor:
+ */
+ if (num_rows > upsample->rows_to_go)
+ num_rows = upsample->rows_to_go;
+ /* And not more than what the client can accept: */
+ out_rows_avail -= *out_row_ctr;
+ if (num_rows > out_rows_avail)
+ num_rows = out_rows_avail;
+
+ (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
+ (JDIMENSION) upsample->next_row_out,
+ output_buf + *out_row_ctr,
+ (int) num_rows);
+
+ /* Adjust counts */
+ *out_row_ctr += num_rows;
+ upsample->rows_to_go -= num_rows;
+ upsample->next_row_out += num_rows;
+ /* When the buffer is emptied, declare this input row group consumed */
+ if (upsample->next_row_out >= cinfo->max_v_samp_factor)
+ (*in_row_group_ctr)++;
+}
+
+
+/*
+ * These are the routines invoked by sep_upsample to upsample pixel values
+ * of a single component. One row group is processed per call.
+ */
+
+
+/*
+ * For full-size components, we just make color_buf[ci] point at the
+ * input buffer, and thus avoid copying any data. Note that this is
+ * safe only because sep_upsample doesn't declare the input row group
+ * "consumed" until we are done color converting and emitting it.
+ */
+
+METHODDEF(void)
+fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ *output_data_ptr = input_data;
+}
+
+
+/*
+ * This is a no-op version used for "uninteresting" components.
+ * These components will not be referenced by color conversion.
+ */
+
+METHODDEF(void)
+noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ *output_data_ptr = NULL; /* safety check */
+}
+
+
+/*
+ * This version handles any integral sampling ratios.
+ * This is not used for typical JPEG files, so it need not be fast.
+ * Nor, for that matter, is it particularly accurate: the algorithm is
+ * simple replication of the input pixel onto the corresponding output
+ * pixels. The hi-falutin sampling literature refers to this as a
+ * "box filter". A box filter tends to introduce visible artifacts,
+ * so if you are actually going to use 3:1 or 4:1 sampling ratios
+ * you would be well advised to improve this code.
+ */
+
+METHODDEF(void)
+int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
+ JSAMPARRAY output_data = *output_data_ptr;
+ register JSAMPROW inptr, outptr;
+ register JSAMPLE invalue;
+ register int h;
+ JSAMPROW outend;
+ int h_expand, v_expand;
+ int inrow, outrow;
+
+ h_expand = upsample->h_expand[compptr->component_index];
+ v_expand = upsample->v_expand[compptr->component_index];
+
+ inrow = outrow = 0;
+ while (outrow < cinfo->max_v_samp_factor) {
+ /* Generate one output row with proper horizontal expansion */
+ inptr = input_data[inrow];
+ outptr = output_data[outrow];
+ outend = outptr + cinfo->output_width;
+ while (outptr < outend) {
+ invalue = *inptr++; /* don't need GETJSAMPLE() here */
+ for (h = h_expand; h > 0; h--) {
+ *outptr++ = invalue;
+ }
+ }
+ /* Generate any additional output rows by duplicating the first one */
+ if (v_expand > 1) {
+ jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
+ v_expand-1, cinfo->output_width);
+ }
+ inrow++;
+ outrow += v_expand;
+ }
+}
+
+
+/*
+ * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
+ * It's still a box filter.
+ */
+
+METHODDEF(void)
+h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ JSAMPARRAY output_data = *output_data_ptr;
+ register JSAMPROW inptr, outptr;
+ register JSAMPLE invalue;
+ JSAMPROW outend;
+ int inrow;
+
+ for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
+ inptr = input_data[inrow];
+ outptr = output_data[inrow];
+ outend = outptr + cinfo->output_width;
+ while (outptr < outend) {
+ invalue = *inptr++; /* don't need GETJSAMPLE() here */
+ *outptr++ = invalue;
+ *outptr++ = invalue;
+ }
+ }
+}
+
+
+/*
+ * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
+ * It's still a box filter.
+ */
+
+METHODDEF(void)
+h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ JSAMPARRAY output_data = *output_data_ptr;
+ register JSAMPROW inptr, outptr;
+ register JSAMPLE invalue;
+ JSAMPROW outend;
+ int inrow, outrow;
+
+ inrow = outrow = 0;
+ while (outrow < cinfo->max_v_samp_factor) {
+ inptr = input_data[inrow];
+ outptr = output_data[outrow];
+ outend = outptr + cinfo->output_width;
+ while (outptr < outend) {
+ invalue = *inptr++; /* don't need GETJSAMPLE() here */
+ *outptr++ = invalue;
+ *outptr++ = invalue;
+ }
+ jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
+ 1, cinfo->output_width);
+ inrow++;
+ outrow += 2;
+ }
+}
+
+
+/*
+ * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
+ *
+ * The upsampling algorithm is linear interpolation between pixel centers,
+ * also known as a "triangle filter". This is a good compromise between
+ * speed and visual quality. The centers of the output pixels are 1/4 and 3/4
+ * of the way between input pixel centers.
+ *
+ * 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_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ JSAMPARRAY output_data = *output_data_ptr;
+ register JSAMPROW inptr, outptr;
+ register int invalue;
+ register JDIMENSION colctr;
+ int inrow;
+
+ for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
+ inptr = input_data[inrow];
+ outptr = output_data[inrow];
+ /* Special case for first column */
+ invalue = GETJSAMPLE(*inptr++);
+ *outptr++ = (JSAMPLE) invalue;
+ *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
+
+ for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
+ /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
+ invalue = GETJSAMPLE(*inptr++) * 3;
+ *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
+ *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
+ }
+
+ /* Special case for last column */
+ invalue = GETJSAMPLE(*inptr);
+ *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
+ *outptr++ = (JSAMPLE) invalue;
+ }
+}
+
+
+/*
+ * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
+ * Again a triangle filter; see comments for h2v1 case, above.
+ *
+ * It is OK for us to reference the adjacent input rows because we demanded
+ * context from the main buffer controller (see initialization code).
+ */
+
+METHODDEF(void)
+h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
+ JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
+{
+ JSAMPARRAY output_data = *output_data_ptr;
+ register JSAMPROW inptr0, inptr1, outptr;
+#if BITS_IN_JSAMPLE == 8
+ register int thiscolsum, lastcolsum, nextcolsum;
+#else
+ register INT32 thiscolsum, lastcolsum, nextcolsum;
+#endif
+ register JDIMENSION colctr;
+ int inrow, outrow, v;
+
+ inrow = outrow = 0;
+ while (outrow < cinfo->max_v_samp_factor) {
+ for (v = 0; v < 2; v++) {
+ /* inptr0 points to nearest input row, inptr1 points to next nearest */
+ inptr0 = input_data[inrow];
+ if (v == 0) /* next nearest is row above */
+ inptr1 = input_data[inrow-1];
+ else /* next nearest is row below */
+ inptr1 = input_data[inrow+1];
+ outptr = output_data[outrow++];
+
+ /* Special case for first column */
+ thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
+ nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
+ *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
+ *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
+ lastcolsum = thiscolsum; thiscolsum = nextcolsum;
+
+ for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
+ /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
+ /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
+ nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
+ *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
+ *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
+ lastcolsum = thiscolsum; thiscolsum = nextcolsum;
+ }
+
+ /* Special case for last column */
+ *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
+ *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
+ }
+ inrow++;
+ }
+}
+
+
+/*
+ * Module initialization routine for upsampling.
+ */
+
+GLOBAL(void)
+jinit_upsampler (j_decompress_ptr cinfo)
+{
+ my_upsample_ptr upsample;
+ int ci;
+ jpeg_component_info * compptr;
+ boolean need_buffer, do_fancy;
+ int h_in_group, v_in_group, h_out_group, v_out_group;
+
+ upsample = (my_upsample_ptr)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ SIZEOF(my_upsampler));
+ cinfo->upsample = (struct jpeg_upsampler *) upsample;
+ upsample->pub.start_pass = start_pass_upsample;
+ upsample->pub.upsample = sep_upsample;
+ upsample->pub.need_context_rows = FALSE; /* until we find out differently */
+
+ if (cinfo->CCIR601_sampling) /* this isn't supported */
+ ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
+
+ /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
+ * so don't ask for it.
+ */
+ do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;
+
+ /* Verify we can handle the sampling factors, select per-component methods,
+ * and create storage as needed.
+ */
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ /* Compute size of an "input group" after IDCT scaling. This many samples
+ * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
+ */
+ h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size;
+ v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size;
+ h_out_group = cinfo->max_h_samp_factor;
+ v_out_group = cinfo->max_v_samp_factor;
+ upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
+ need_buffer = TRUE;
+ if (! compptr->component_needed) {
+ /* Don't bother to upsample an uninteresting component. */
+ upsample->methods[ci] = noop_upsample;
+ need_buffer = FALSE;
+ } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
+ /* Fullsize components can be processed without any work. */
+ upsample->methods[ci] = fullsize_upsample;
+ need_buffer = FALSE;
+ } else if (h_in_group * 2 == h_out_group &&
+ v_in_group == v_out_group) {
+ /* Special cases for 2h1v upsampling */
+ if (do_fancy && compptr->downsampled_width > 2)
+ upsample->methods[ci] = h2v1_fancy_upsample;
+ else
+ upsample->methods[ci] = h2v1_upsample;
+ } else if (h_in_group * 2 == h_out_group &&
+ v_in_group * 2 == v_out_group) {
+ /* Special cases for 2h2v upsampling */
+ if (do_fancy && compptr->downsampled_width > 2) {
+ upsample->methods[ci] = h2v2_fancy_upsample;
+ upsample->pub.need_context_rows = TRUE;
+ } else
+ upsample->methods[ci] = h2v2_upsample;
+ } else if ((h_out_group % h_in_group) == 0 &&
+ (v_out_group % v_in_group) == 0) {
+ /* Generic integral-factors upsampling method */
+ upsample->methods[ci] = int_upsample;
+ upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
+ upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
+ } else
+ ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
+ if (need_buffer) {
+ upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
+ ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ (JDIMENSION) jround_up((long) cinfo->output_width,
+ (long) cinfo->max_h_samp_factor),
+ (JDIMENSION) cinfo->max_v_samp_factor);
+ }
+ }
+}
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