devkitPro

Posted: **Tue Dec 09, 2008 2:56 pm**

I am writing a simple app for the DS that loads jpegs from cart (via libfat) and then, using Burt Radons JPEG decompression library, displays the result in BG_GFX.

My problem is that this process is too slow (somewhere in the order of 18 seconds). If I link the jpeg directly into the binary using bin2s, however, then the process very quick. Below is some example code:

Code: Select all

 FILE* file = fopen("files/my_image.jpg", "rb");
 uint8* buffer1 = new uint8[256*192*4];
 uint16* buffer2 = new uint16[256*192*4];

 while (!feof(file)){
     fread(buffer1, sizeof(unsigned char), 1, file);
 }

 JPEG_DecompressImage (buffer1, buffer2, 256, 192);
 dmaCopy(buffer2, BG_GFX, 256*192);

So, most excellent code gurus, WTF? Am I doing it wrong?

Thanks

Posted: **Wed Dec 10, 2008 4:35 pm**

*ahem*

I was doing it wrong

instead of messing about with a while loop, just read the file into the buffer thus:

Code: Select all

    //get file size
    fseek(file, 0L, SEEK_END);
    int size = ftell(file);
    fseek(file, 0L, SEEK_SET);

    //allocate buffers
    unsigned char* buffer1 = new unsigned char[size];
    uint16* buffer2 = new uint16[256*192*2];

    //read file into buffer
    fread(buffer1, sizeof(unsigned char), size, file);

    //decompress the JPEG
    JPEG_DecompressImage (buffer1, buffer2, 256, 192);

    //copy to VRAM
    memmove(BG_GFX, buffer2, 256*192);

See, aint that easy?

*sheesh*

Posted: **Sat Mar 14, 2009 2:22 pm**

Hello,
I need to know if you could show here your code about how to load jpeg image into devkitpro because bmp image have big size. Besides I want to know if the quality of your image is good. Thx

devkitPro

JPEG decompression from main memory into VRAM is slow. FIXED

JPEG decompression from main memory into VRAM is slow. FIXED

Re: JPEG decompression from main memory into VRAM is slow. why?

Re: JPEG decompression from main memory into VRAM is slow. FIXED