核心代码：
int start = QDateTime::currentDateTime().currentMSecsSinceEpoch();
QPixmap image = screen->grabWindow(0);
QBuffer buffer;
// qDebug()<<_pixWidth<<_pixHeight;
image = image.scaled(_pixWidth,_pixHeight,Qt::IgnoreAspectRatio,Qt::SmoothTransformation);
image.save(&buffer,"JPEG");
qDebug()<<image.save("C:\\Users\\9DVR\\Desktop\\four\\quantized_b.jpg","jpg");
int end = QDateTime::currentDateTime().currentMSecsSinceEpoch();
qDebug()<<start<<end<<end-start;
time->stop();
return;
unsigned int width, height;
unsigned char *raw_rgba_pixels;
unsigned int status = lodepng_decode32(&raw_rgba_pixels, &width, &height, (unsigned char*)buffer.data().data(),buffer.size());
if (status) {
qDebug()<<"load image error:"<<lodepng_error_text(status);
return;
}
liq_attr *handle = liq_attr_create();
liq_image *input_image = liq_image_create_rgba(handle, raw_rgba_pixels, width, height, 0);
liq_set_quality(handle,50,60);
liq_result *quantization_result = NULL;
quantization_result = liq_quantize_image(handle, input_image) ;
if (quantization_result == NULL) {
qDebug()<< "Quantization failed\n";
return ;
}
size_t pixels_size = width * height;
unsigned char *raw_8bit_pixels = (unsigned char *)malloc(pixels_size);
liq_set_dithering_level(quantization_result, 1.0);
liq_write_remapped_image(quantization_result, input_image, raw_8bit_pixels, pixels_size);
const liq_palette *palette = liq_get_palette(quantization_result);
LodePNGState state;
lodepng_state_init(&state);
state.info_raw.colortype = LCT_PALETTE;
state.info_raw.bitdepth = 8;
state.info_png.color.colortype = LCT_PALETTE;
state.info_png.color.bitdepth = 8;
for(int i=0; i < palette->count; i++) {
lodepng_palette_add(&state.info_png.color, palette->entries[i].r, palette->entries[i].g, palette->entries[i].b, palette->entries[i].a);
lodepng_palette_add(&state.info_raw, palette->entries[i].r, palette->entries[i].g, palette->entries[i].b, palette->entries[i].a);
}
unsigned char *output_file_data;
size_t output_file_size;
unsigned int out_status = lodepng_encode(&output_file_data, &output_file_size, raw_8bit_pixels, width, height, &state);
if (out_status) {
qDebug()<<"Can't encode image:"<<lodepng_error_text(out_status);
return ;
}
liq_result_destroy(quantization_result);
liq_image_destroy(input_image);
liq_attr_destroy(handle);
free(raw_8bit_pixels);
lodepng_state_cleanup(&state);
buffer.data().data();
ImageData img ;
img.size = output_file_size;
memset(img.imgData,0,sizeof(img.imgData));
memcpy(img.imgData,output_file_data,output_file_size);