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POHaving trouble with SDL_GetRGBA
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9477386
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1
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2012-02-28T06:23:50.757
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2012-03-06T04:50:13.960
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569
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<p>I'm trying to use SDL_GetRGBA to display the RGBA values of the pixels of an image, however I can't get it to work. Here is my code and output:</p> <pre><code>#include <stdio.h> #include <SDL/SDL.h> int main() { SDL_Surface *screen; SDL_Surface *image; SDL_Init(SDL_INIT_VIDEO); screen = SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE); image = SDL_LoadBMP("testimg2.bmp"); Uint32 i,j; Uint8 r, g, b, a; Uint8 *p = (Uint8 *) image->pixels; for (i=0; i < 300; i++) { for (j=0; j < 4; j++) printf("i = %u, image->pixels[i*4+%u] = %u\n", i, j, p[i*4+j]); SDL_GetRGBA(i, image->format, &b, &g, &r, &a); printf("i = %u, r = %u, g = %u, b = %u, a = %u\n", i, r, g, b, a); } SDL_BlitSurface(image, NULL, screen, NULL); SDL_Flip(screen); SDL_Delay(2000); SDL_FreeSurface(image); SDL_Quit(); return 0; } i = 0, image->pixels[i*4+0] = 0 i = 0, image->pixels[i*4+1] = 0 i = 0, image->pixels[i*4+2] = 255 i = 0, image->pixels[i*4+3] = 133 i = 0, r = 0, g = 0, b = 0, a = 255 i = 1, image->pixels[i*4+0] = 0 i = 1, image->pixels[i*4+1] = 0 i = 1, image->pixels[i*4+2] = 255 i = 1, image->pixels[i*4+3] = 140 i = 1, r = 1, g = 0, b = 0, a = 255 i = 2, image->pixels[i*4+0] = 0 i = 2, image->pixels[i*4+1] = 0 i = 2, image->pixels[i*4+2] = 255 i = 2, image->pixels[i*4+3] = 132 i = 2, r = 2, g = 0, b = 0, a = 255 i = 3, image->pixels[i*4+0] = 0 i = 3, image->pixels[i*4+1] = 0 i = 3, image->pixels[i*4+2] = 255 i = 3, image->pixels[i*4+3] = 118 i = 3, r = 3, g = 0, b = 0, a = 255 i = 4, image->pixels[i*4+0] = 0 i = 4, image->pixels[i*4+1] = 0 i = 4, image->pixels[i*4+2] = 255 i = 4, image->pixels[i*4+3] = 114 i = 4, r = 4, g = 0, b = 0, a = 255 i = 5, image->pixels[i*4+0] = 0 i = 5, image->pixels[i*4+1] = 0 i = 5, image->pixels[i*4+2] = 255 i = 5, image->pixels[i*4+3] = 115 i = 5, r = 5, g = 0, b = 0, a = 255 </code></pre> <p>So everything seems to be correct when manually going through the pixel array byte by byte, but the SDL_GetRGBA function seems to be returning incorrect values. I'm not sure what I'm doing wrong.</p>
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Having trouble with SDL_GetRGBA
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