Does GPUJPEG support saving BMP files as PNG format?Is the encoding and decoding implemented within the GPU?for NVIDIA GPUs

[libaineu2004]

1.Does GPUJPEG support saving BMP files as PNG format?Is the encoding and decoding implemented within the GPU?for NVIDIA GPUs
Thanks!

2.The support for png has already been added in
0871ce9
I saw the submission, but i don't know how to using the new png function interface.

3.Could you provide a similar example?
If I want to save it as a PNG file, how should I specify the following parameters?
param_image.color_space = GPUJPEG_YCBCR_JPEG;
param_image.pixel_format = GPUJPEG_U8;

https://github.com/CESNET/GPUJPEG/blob/master/examples/encode_minimal.c
// Minimal encoding sample.
#include <assert.h>
#include <libgpujpeg/gpujpeg_encoder.h>
#include <stdio.h>
#include <stdlib.h>

#define OUT_FNAME "out.jpg"

int
main()
{
    struct gpujpeg_encoder *encoder = gpujpeg_encoder_create(0);
    assert(encoder != NULL);
    struct gpujpeg_parameters param;
    gpujpeg_set_default_parameters(&param);
    struct gpujpeg_image_parameters param_image;
    gpujpeg_image_set_default_parameters(&param_image);
    param_image.width = 640;
    param_image.height = 480;
    param_image.color_space = GPUJPEG_YCBCR_JPEG;
    param_image.pixel_format = GPUJPEG_U8;
    struct gpujpeg_encoder_input encoder_input;
    uint8_t *blank_buffer =
        calloc(1, gpujpeg_image_calculate_size(&param_image));
    gpujpeg_encoder_input_set_image(&encoder_input, blank_buffer);
    uint8_t *out = NULL;
    size_t len = 0;
    gpujpeg_encoder_encode(encoder, &param, &param_image, &encoder_input, &out,
                           &len);
    FILE *outf = fopen(OUT_FNAME, "wb");
    fwrite(out, len, 1, outf);
    printf("Ouput " OUT_FNAME " was written.\n");
    fclose(outf);
    free(blank_buffer);
    gpujpeg_encoder_destroy(encoder);
}

[MartinPulec]

You mean encoding BMP directly to PNG? Unfortunately this is not possible - GPUJPEG is intended for encoding/decoding JPEGs.

This means that although you can encode from BMP/PNG to JPEG or decode from JPEG to BMP (or transcode from JPEG to PNG), BMP<->PNG conversions are not supported.

Is the encoding and decoding implemented within the GPU?

• encoding/decoding JPEGs from/to RAW - of course (this is the aim of this library)
• PNG - no
• (BMP is trivial even on CPU)

The formats BMP and PNG are implemented via stb_image (as well as TGA and GIF are) so those are CPU only. Mainly PNG and GIF is there mostly for convenience - because are not accelerated and its encode/decode will perhaps consume some time. The main purpose of GPUJPEG is to compress/decompress JPEG from/to RAW bitmap.

If you are looking for accelerated PNG encoder/decoder. you can look here - to view the PDF, registration is needed, but basically a takeaway is that they at NVIDIA managed to speed-up encoding of PNG up to 20x (compared to CPU implementation). for decoding at most x2 (but also slower). IIRC it should be implemented inside NVIDIA DALI.

[libaineu2004]

Thank you!
The performance of stb_image in reading and writing png files is still a bit slow.
I found a library of the CPU, https://github.com/richgel999/fpng, is relatively fast.
But I would rather find an open-source library that can use GPU to encode and decode png files.