X11 でスクリーンキャプチャー その2
32bpp, 16bpp, 8bpp, まで対応してみる．暇なのか？
しかし結局手元の環境で 8bpp の場合に正常な絵をキャプチャすることはできませんでしたとさ．
16bpp だとこんな絵が撮れます．
しかし 8bpp だとこんな絵になってしまいます．
問01 8bpp の絵が変なのは何が間違っているのでしょうか？
以下コード．
/************************************************************
* gcc capture_screen_x11-02.c -L/usr/X11R6/lib -lX11
************************************************************/
#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <assert.h>
#define IMAGE_FILE_PATH "capture_screen_x11.ppm"
int mask2shiftbit(unsigned long mask)
{
int result = -1;
int i;
const int bits = sizeof(unsigned long) * 8;
const unsigned long msb = 1 << (bits-1);
for (i = 0;i < bits;i++)
{
if (mask & msb)
{
result = bits - 8 - i;
break;
}
mask <<= 1;
}
return result;
}
static
void write32bppXImageToP3File(XImage *image, const char *file_path)
{
FILE *file;
assert(image != NULL);
assert(image->bits_per_pixel == 32);
assert(file_path != NULL);
file = fopen(file_path, "wb");
if (file != NULL)
{
int x, y;
uint8_t *datap;
int red_shift, green_shift, blue_shift;
red_shift = mask2shiftbit(image->red_mask);
green_shift = mask2shiftbit(image->green_mask);
blue_shift = mask2shiftbit(image->blue_mask);
fprintf(file, "P3\n");
fprintf(file, "%d %d\n", image->width, image->height);
fprintf(file, "255\n");
for (y = 0;y < image->height;y++)
{
datap = (uint8_t *)(image->data + y * image->bytes_per_line);
for (x = 0;x < image->width;x++)
{
uint32_t pixel;
pixel = *(uint32_t *)datap;
fprintf(file, "%lu %lu %lu ",
(pixel & image->red_mask) >> red_shift,
(pixel & image->green_mask) >> green_shift,
(pixel & image->blue_mask) >> blue_shift);
datap += 4;
}
fprintf(file, "\n");
}
fclose(file);
}
}
static
void write16bppXImageToP3File(XImage *image, const char *file_path)
{
FILE *file;
assert(image != NULL);
assert(image->bits_per_pixel == 16);
assert(file_path != NULL);
file = fopen(file_path, "wb");
if (file != NULL)
{
int x, y;
uint8_t *datap;
int red_shift, green_shift, blue_shift;
red_shift = mask2shiftbit(image->red_mask);
green_shift = mask2shiftbit(image->green_mask);
blue_shift = mask2shiftbit(image->blue_mask);
fprintf(file, "P3\n");
fprintf(file, "%d %d\n", image->width, image->height);
fprintf(file, "255\n");
for (y = 0;y < image->height;y++)
{
datap = (uint8_t *)(image->data + y * image->bytes_per_line);
for (x = 0;x < image->width;x++)
{
unsigned long r, g, b;
uint16_t pixel;
pixel = *(uint16_t *)datap;
r = pixel & image->red_mask;
g = pixel & image->green_mask;
b = pixel & image->blue_mask;
r = red_shift >= 0 ? r >> red_shift : r << -red_shift;
g = green_shift >= 0 ? g >> green_shift : g << -green_shift;
b = blue_shift >= 0 ? b >> blue_shift : b << -blue_shift;
fprintf(file, "%lu %lu %lu ", r, g, b);
datap += 2;
}
fprintf(file, "\n");
}
fclose(file);
}
}
static
void write8bppXImageToP3File(XImage *image, XColor *colors, const char *file_path)
{
FILE *file;
assert(image != NULL);
assert(image->bits_per_pixel == 8);
assert(file_path != NULL);
file = fopen(file_path, "wb");
if (file != NULL)
{
int x, y;
uint8_t *datap;
fprintf(file, "P3\n");
fprintf(file, "%d %d\n", image->width, image->height);
fprintf(file, "255\n");
for (y = 0;y < image->height;y++)
{
datap = ((uint8_t *)image->data + (y * image->bytes_per_line));
for (x = 0;x < image->width;x++)
{
XColor color;
uint8_t pixel;
pixel = *datap;
color = colors[pixel];
fprintf(file, "%u %u %u ", color.red >> 8,
color.green >> 8, color.blue >> 8);
datap += 1;
}
fprintf(file, "\n");
fflush(file);
}
fclose(file);
}
}
int main(int argc, char* argv[])
{
Display* display;
int screen;
Window rootWindow;
XWindowAttributes attributes;
int width, height;
XImage *image;
display = XOpenDisplay("");
screen = DefaultScreen(display);
rootWindow = RootWindow(display, screen);
XGetWindowAttributes(display, rootWindow, &attributes);
width = attributes.width;
height = attributes.height;
image = XGetImage(display, rootWindow,
0, 0, width, height,
AllPlanes, ZPixmap);
if (image != NULL)
{
switch (image->bits_per_pixel)
{
case 32 :
write32bppXImageToP3File(image, IMAGE_FILE_PATH);
break;
case 16 :
write16bppXImageToP3File(image, IMAGE_FILE_PATH);
break;
case 8 :
{
int i, num_colors;;
XColor *colors;
num_colors = attributes.visual->map_entries;
colors = (XColor *)malloc(sizeof(XColor) * num_colors);
for (i = 0;i < num_colors;i++) colors[i].pixel = i;
XQueryColors(display, attributes.colormap, colors, num_colors);
write8bppXImageToP3File(image, colors, IMAGE_FILE_PATH);
free(colors);
}
break;
default:
fprintf(stderr, "Not supported image : bits_per_pixel = %d\n", image->bits_per_pixel);
break;
}
XFree(image);
}
XCloseDisplay(display);
return 0;
}以下試した環境．
ところで Colormap を処理するかどうかの分岐は Visual class を見るべきなのかなぁ…？
