| /* |
| * jcsample.c |
| * |
| * Copyright (C) 1991, 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 subsampling routines. |
| * These routines are invoked via the subsample and |
| * subsample_init/term methods. |
| */ |
| |
| #include "jinclude.h" |
| |
| |
| /* |
| * Initialize for subsampling a scan. |
| */ |
| |
| METHODDEF void |
| subsample_init (compress_info_ptr cinfo) |
| { |
| /* no work for now */ |
| } |
| |
| |
| /* |
| * Subsample pixel values of a single component. |
| * This version only handles integral sampling ratios. |
| */ |
| |
| METHODDEF void |
| subsample (compress_info_ptr cinfo, int which_component, |
| long input_cols, int input_rows, |
| long output_cols, int output_rows, |
| JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below, |
| JSAMPARRAY output_data) |
| { |
| jpeg_component_info * compptr = cinfo->cur_comp_info[which_component]; |
| int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v; |
| long outcol; |
| JSAMPROW inptr, outptr; |
| INT32 outvalue; |
| |
| /* TEMP FOR DEBUGGING PIPELINE CONTROLLER */ |
| if (output_rows != compptr->v_samp_factor || |
| input_rows != cinfo->max_v_samp_factor || |
| (output_cols % compptr->h_samp_factor) != 0 || |
| (input_cols % cinfo->max_h_samp_factor) != 0 || |
| input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor) |
| ERREXIT(cinfo->emethods, "Bogus subsample parameters"); |
| |
| 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; |
| |
| inrow = 0; |
| for (outrow = 0; outrow < output_rows; outrow++) { |
| outptr = output_data[outrow]; |
| for (outcol = 0; outcol < output_cols; outcol++) { |
| outvalue = 0; |
| for (v = 0; v < v_expand; v++) { |
| inptr = input_data[inrow+v] + (outcol*h_expand); |
| for (h = 0; h < h_expand; h++) { |
| outvalue += GETJSAMPLE(*inptr++); |
| } |
| } |
| *outptr++ = (outvalue + numpix2) / numpix; |
| } |
| inrow += v_expand; |
| } |
| } |
| |
| |
| /* |
| * Subsample pixel values of a single component. |
| * This version handles the special case of a full-size component. |
| */ |
| |
| METHODDEF void |
| fullsize_subsample (compress_info_ptr cinfo, int which_component, |
| long input_cols, int input_rows, |
| long output_cols, int output_rows, |
| JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below, |
| JSAMPARRAY output_data) |
| { |
| if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */ |
| ERREXIT(cinfo->emethods, "Pipeline controller messed up"); |
| |
| jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols); |
| } |
| |
| |
| /* |
| * Clean up after a scan. |
| */ |
| |
| METHODDEF void |
| subsample_term (compress_info_ptr cinfo) |
| { |
| /* no work for now */ |
| } |
| |
| |
| |
| /* |
| * The method selection routine for subsampling. |
| * Note that we must select a routine for each component. |
| */ |
| |
| GLOBAL void |
| jselsubsample (compress_info_ptr cinfo) |
| { |
| short ci; |
| jpeg_component_info * compptr; |
| |
| if (cinfo->CCIR601_sampling) |
| ERREXIT(cinfo->emethods, "CCIR601 subsampling not implemented yet"); |
| |
| for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
| compptr = cinfo->cur_comp_info[ci]; |
| if (compptr->h_samp_factor == cinfo->max_h_samp_factor && |
| compptr->v_samp_factor == cinfo->max_v_samp_factor) |
| cinfo->methods->subsample[ci] = fullsize_subsample; |
| else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 && |
| (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) |
| cinfo->methods->subsample[ci] = subsample; |
| else |
| ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet"); |
| } |
| |
| cinfo->methods->subsample_init = subsample_init; |
| cinfo->methods->subsample_term = subsample_term; |
| } |