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main.cpp
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main.cpp
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// Convert a .bmp file (from a high-compression jpg, as from a very cheap camera)
// into another .bmp file with greatly attenuated 8x8-pixel-block jpg artifacts.
extern "C" {
#include "costella_unblock.h"
}
#include "EasyBMP.h"
#include <png.h>
#include <algorithm>
#include <cstdlib>
struct rgbpixel {unsigned char r,g,b; };
// Actually YCbCr, not YUV.
// From www.equasys.de/colorconversion.html YCbCr - RGB.
// (It might also work to use R,G,B directly, each pretending to be Y of YUV.)
void YUVfromRGB(double& Y, double& U, double& V, const double R, const double G, const double B)
{
Y = 0.257 * R + 0.504 * G + 0.098 * B + 16;
U = -0.148 * R - 0.291 * G + 0.439 * B + 128;
V = 0.439 * R - 0.368 * G - 0.071 * B + 128;
}
void RGBfromYUV(double& R, double& G, double& B, double Y, double U, double V)
{
Y -= 16;
U -= 128;
V -= 128;
R = 1.164 * Y + 1.596 * V;
G = 1.164 * Y - 0.392 * U - 0.813 * V;
B = 1.164 * Y + 2.017 * U;
}
std::string filenameExtension(const std::string& s)
{
const std::string::size_type i = s.find_last_of(".");
if (i == std::string::npos)
return "";
std::string ext(s.substr(i + 1));
std::transform(ext.begin(), ext.end(), ext.begin(), ::tolower);
return ext;
}
int main( int argc, char** argv)
{
if (argc != 3) {
printf("usage: %s in.[bmp|png] out.[bmp|png]\n", argv[0]);
return 1;
}
if (filenameExtension(argv[1]) != filenameExtension(argv[2]))
printf("%s: warning: filenames %s and %s have different extensions.\n", argv[0], argv[1], argv[2]);
const bool fPNG = filenameExtension(argv[1]) == "png";
int w, h;
FILE *fp;
struct rgbpixel **ppRowPNG = NULL;
png_structp pPNG;
png_infop pInfoPNG;
BMP bmp;
if (fPNG) {
fp = fopen(argv[1], "rb");
pPNG = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
pInfoPNG = png_create_info_struct(pPNG);
png_init_io(pPNG, fp);
png_read_png(pPNG, pInfoPNG, PNG_TRANSFORM_STRIP_ALPHA|PNG_TRANSFORM_EXPAND|PNG_TRANSFORM_STRIP_16, NULL);
ppRowPNG = (struct rgbpixel**)png_get_rows(pPNG, pInfoPNG);
w = png_get_image_width(pPNG, pInfoPNG);
h = png_get_image_height(pPNG, pInfoPNG);
png_destroy_read_struct(&pPNG, NULL, NULL);
fclose(fp);
} else {
bmp.ReadFromFile(argv[1]);
w = bmp.TellWidth();
h = bmp.TellHeight();
}
// Convert bmp.rgb_data or ppRowPNG to YUV color planes.
const unsigned cb = w * h;
unsigned char bufY[cb];
unsigned char bufU[cb];
unsigned char bufV[cb];
int y,x;
int i=0;
for (y = 0; y < h; ++y) {
for (x = 0; x < w; ++x,++i) {
double R,G,B;
if (fPNG) {
const rgbpixel rgb = ppRowPNG[y][x];
R = rgb.r;
G = rgb.g;
B = rgb.b;
} else {
const RGBApixel* rgb = bmp(x,y);
R = rgb->Red;
G = rgb->Green;
B = rgb->Blue;
}
double Y,U,V;
YUVfromRGB(Y,U,V,R,G,B);
#undef testing
#ifdef testing
double a,b,c;
RGBfromYUV(a,b,c,Y,U,V);
if (fabs(a-R) + fabs(b-G) + fabs(c-B) > 0.9 /* in the scale 0.0 to 255.0 */ )
printf("not inverses.\n");
// but that's two linear operators, before the necessary clamping.
#endif
// Clamp to 0..255.
bufY[i] = COSTELLA_IMAGE_LIMIT_RANGE(Y);
bufU[i] = COSTELLA_IMAGE_LIMIT_RANGE(U);
bufV[i] = COSTELLA_IMAGE_LIMIT_RANGE(V);
}
}
COSTELLA_IMAGE im;
im.bAlpha = 0;
im.bRgb = 0;
im.udHeight = h;
im.udWidth = w; // may fail if not a multiple of 16
im.sdRowStride = w; // maybe something about bufPitch, width bumped up to multiple of 16.
im.sdAlphaRowStride = 0;
#if 0
// Unblock only luma (bufY).
im.bColor = im.bDownsampledChrominance = im.bNonreplicatedDownsampledChrominance = 0;
im.ig = bufY /* COSTELLA_IMAGE_GRAY */;
#else
// Unblock luma, Cb, and Cr.
im.bColor = im.bDownsampledChrominance = im.bNonreplicatedDownsampledChrominance = 1;
im.ic.aubRY = bufY;
im.ic.aubGCb = bufU;
im.ic.aubBCr = bufV;
#endif
costella_unblock_initialize(stdout);
const int fPhoto = 0; // API docs suggest 1, but that boosts ringing of high-contrast detail (timestamps, windows of buildings).
// (Internal mucking about, in costella_unblock.c bConservativePhotographic tweaking udCumMeasuredConservative,
// had either no effect or caused a segfault.)
int ok = costella_unblock(&im, &im, fPhoto, 0, NULL, NULL, 0);
if (!ok)
printf("%s: problem during costella_unblock().\n", argv[0]);
costella_unblock_finalize(stdout);
// Convert bufY, bufU, bufV back into a bmp.
// (Or, set im.bRgb=1 to avoid this conversion? That sets bOutYCbCr in CostellaUnblock(),
// which causes calls to CostellaImageConvertRgbToYcbcr() and CostellaImageConvertYcbcrToRgb().
// Those call macros like COSTELLA_IMAGE_CONVERT_RGB_TO_YCBCR(),
// which lookup tables like gasdCostellaImageConvertRCb[] for Red to Cb.)
i=0;
for (y = 0; y < h; ++y) {
for (x = 0; x < w; ++x,++i) {
double R,G,B;
RGBfromYUV(R,G,B, bufY[i], bufU[i], bufV[i]);
if (fPNG) {
ppRowPNG[y][x] = (rgbpixel){
COSTELLA_IMAGE_LIMIT_RANGE(R),
COSTELLA_IMAGE_LIMIT_RANGE(G),
COSTELLA_IMAGE_LIMIT_RANGE(B) };
} else {
RGBApixel* rgb = bmp(x,y);
rgb->Red = COSTELLA_IMAGE_LIMIT_RANGE(R);
rgb->Green = COSTELLA_IMAGE_LIMIT_RANGE(G);
rgb->Blue = COSTELLA_IMAGE_LIMIT_RANGE(B);
}
}
}
if (fPNG) {
fp = fopen(argv[2], "wb");
pPNG = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
png_init_io(pPNG, fp);
png_set_rows(pPNG, pInfoPNG, (png_bytepp)ppRowPNG);
png_write_png(pPNG, pInfoPNG, PNG_TRANSFORM_IDENTITY, NULL);
png_destroy_write_struct(&pPNG, &pInfoPNG);
fclose(fp);
} else {
bmp.WriteToFile(argv[2]);
}
return 0;
}