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Laurence BankLaurence Bank
Laurence Bank
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Laurence Bank
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Added more support in RGB565 output for alpha blending of grayscale and indexed color. Added more functional tests for those features
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4 files changed

+1815
-27
lines changed

4 files changed

+1815
-27
lines changed

‎MacOS/PNG_Test/PNG_Test.xcodeproj/project.xcworkspace/xcuserdata/laurencebank.xcuserdatad/UserInterfaceState.xcuserstate‎

1.18 KB
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‎MacOS/PNG_Test/PNG_Test/main.cpp‎

Lines changed: 51 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -20,11 +20,16 @@
2020
#include "../../../src/PNGdec.cpp"
2121

2222
#include "../../../test_images/octocat_8bpp.h"
23+
#include "../../../test_images/octocat.h"
2324
PNG png;
2425
int xoff, yoff, iBpp;
2526
int iWidth, iLines;
2627
uint32_t palentry24;
2728
uint16_t palentry16;
29+
uint32_t u32BG;
30+
uint16_t u16Out;
31+
uint8_t ucPixelType;
32+
2833
//
2934
// Return the current time in microseconds
3035
//
@@ -47,11 +52,17 @@ typedef struct my_private_struct
4752
{
4853
int xoff, yoff; // corner offset
4954
} PRIVATE;
50-
55+
// Second draw callback for testing conversion to RGB565
56+
void PNGDraw2(PNGDRAW *pDraw)
57+
{
58+
uint16_t usPixels[320];
59+
png.getLineAsRGB565(pDraw, usPixels, ucPixelType, u32BG);
60+
if (pDraw->y == 0) { // get first pixel of first line for testing
61+
u16Out = usPixels[0];
62+
}
63+
} /* PNGDraw2() */
5164
void PNGDraw(PNGDRAW *pDraw)
5265
{
53-
//uint16_t usPixels[320];
54-
//uint8_t ucMask[40];
5566
PRIVATE *pPriv = (PRIVATE *)pDraw->pUser;
5667

5768
if (pPriv) {
@@ -66,10 +77,6 @@ PRIVATE *pPriv = (PRIVATE *)pDraw->pUser;
6677
iBpp = pDraw->iBpp;
6778
iWidth = pDraw->iWidth;
6879
iLines++;
69-
// png.getLineAsRGB565(pDraw, usPixels, PNG_RGB565_BIG_ENDIAN, 0xffffffff);
70-
// if (png.getAlphaMask(pDraw, ucMask, 255)) { // if any pixels are opaque, draw them
71-
// spilcdWritePixelsMasked(&lcd, pPriv->xoff, pPriv->yoff + pDraw->y, (uint8_t *)usPixels, ucMask, pDraw->iWidth, DRAW_TO_LCD);
72-
// }
7380
} /* PNGDraw() */
7481

7582
//
@@ -215,6 +222,43 @@ int main(int argc, const char * argv[]) {
215222
PNGLOG(__LINE__, szTestName, " - FAILED");
216223
}
217224
free(pFrameBuffer);
225+
// Test 8 - check 8-bit to RGB565 conversion and alpha blending
226+
ucPixelType = PNG_RGB565_BIG_ENDIAN;
227+
u32BG = 0x00ff00; // set background color to pure green
228+
szTestName = (char *)"PNG Verify 8-bit to RGB565 output";
229+
iTotal++;
230+
PNGLOG(__LINE__, szTestName, szStart);
231+
u16Out = 0xffff;
232+
png.openFLASH((uint8_t *)octocat_8bpp, sizeof(octocat_8bpp), PNGDraw2);
233+
png.setBuffer(NULL);
234+
png.decode(NULL, 0);
235+
png.close();
236+
if (u16Out == 0xe007) { // check transparnet pixel (0,0) to see if it matches the 32-bit BG color we asked for
237+
iTotalPass++;
238+
PNGLOG(__LINE__, szTestName, " - PASSED");
239+
} else {
240+
iTotalFail++;
241+
PNGLOG(__LINE__, szTestName, " - FAILED");
242+
}
243+
// Test 9 - check 32-bit to RGB565 conversion and alpha blending
244+
ucPixelType = PNG_RGB565_BIG_ENDIAN;
245+
u32BG = 0xff0000; // set background color to pure blue
246+
szTestName = (char *)"PNG Verify 32-bit to RGB565 output";
247+
iTotal++;
248+
PNGLOG(__LINE__, szTestName, szStart);
249+
u16Out = 0xffff;
250+
png.openFLASH((uint8_t *)octocat_8bpp, sizeof(octocat_8bpp), PNGDraw2);
251+
png.setBuffer(NULL);
252+
png.decode(NULL, 0);
253+
png.close();
254+
if (u16Out == 0x1f00) { // check transparnet pixel (0,0) to see if it matches the 32-bit BG color we asked for
255+
iTotalPass++;
256+
PNGLOG(__LINE__, szTestName, " - PASSED");
257+
} else {
258+
iTotalFail++;
259+
PNGLOG(__LINE__, szTestName, " - FAILED");
260+
}
261+
218262
// FUZZ testing
219263
// Randomize the input data (file header and compressed data) and confirm that the library returns an error code
220264
// and doesn't have an invalid pointer exception

‎src/png.inl‎

Lines changed: 73 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -241,14 +241,35 @@ PNG_STATIC void PNGRGB565(PNGDRAW *pDraw, uint16_t *pPixels, int iEndiannes, uin
241241

242242
switch (pDraw->iPixelType) {
243243
case PNG_PIXEL_GRAY_ALPHA:
244-
for (x=0; x<pDraw->iWidth; x++) {
245-
c = *s++; // gray level
246-
a = *s++;
247-
j = (a * c) >> 8; // multiply by the alpha
248-
usPixel = usGrayTo565[j];
249-
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
250-
usPixel = __builtin_bswap16(usPixel);
251-
*pDest++ = usPixel;
244+
if (u32Bkgd != 0xffffffff) {
245+
// gray level of background color choice
246+
uint8_t u8BG = (uint8_t)(((u32Bkgd & 0xff) + ((u32Bkgd >> 7) & 0x1fe) + ((u32Bkgd >> 16) & 0xff)) / 4);
247+
uint16_t usBG = usGrayTo565[u8BG];
248+
for (x=0; x<pDraw->iWidth; x++) {
249+
c = *s++; // gray level
250+
a = *s++;
251+
if (a == 0) {
252+
usPixel = usBG;
253+
} else if (a == 255) { // fully opaque
254+
usPixel = usGrayTo565[c];
255+
} else { // mix the colors
256+
usPixel = (c * a) + (u8BG * (255-a));
257+
usPixel = usGrayTo565[(usPixel >> 8)];
258+
}
259+
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
260+
usPixel = __builtin_bswap16(usPixel);
261+
*pDest++ = usPixel;
262+
} // for x
263+
} else {
264+
for (x=0; x<pDraw->iWidth; x++) {
265+
c = *s++; // gray level
266+
a = *s++;
267+
j = (a * c) >> 8; // multiply by the alpha
268+
usPixel = usGrayTo565[j];
269+
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
270+
usPixel = __builtin_bswap16(usPixel);
271+
*pDest++ = usPixel;
272+
}
252273
}
253274
break;
254275
case PNG_PIXEL_GRAYSCALE:
@@ -346,18 +367,50 @@ PNG_STATIC void PNGRGB565(PNGDRAW *pDraw, uint16_t *pPixels, int iEndiannes, uin
346367
switch (pDraw->iBpp) {
347368
case 8: // 8-bit palette also supports palette alpha
348369
if (pDraw->iHasAlpha) { // use the alpha to modify the palette
349-
for (x=0; x<pDraw->iWidth; x++) {
350-
int a;
351-
c = *s++;
352-
a = pDraw->pPalette[768+c]; // get alpha
353-
pPal = &pDraw->pPalette[c * 3];
354-
usPixel = ((pPal[2] * a) >> 11); // blue
355-
usPixel |= (((pPal[1] * a) >> 10) << 5); // green
356-
usPixel |= (((pPal[0] * a) >> 11) << 11); // red
357-
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
358-
usPixel = __builtin_bswap16(usPixel);
359-
*pDest++ = usPixel;
360-
} // for x
370+
if (u32Bkgd != 0xffffffff) { // user wants to blend it with a background color
371+
uint32_t r, g, b, a;
372+
uint32_t b_r, b_g, b_b;
373+
b_r = u32Bkgd & 0xff; b_g = (u32Bkgd & 0xff00) >> 8;
374+
b_b = (u32Bkgd >> 16) & 0xff;
375+
uint16_t u16Clr = (u32Bkgd & 0xf8) << 8;
376+
u16Clr |= ((u32Bkgd & 0xfc00) >> 5);
377+
u16Clr |= ((u32Bkgd & 0xf80000) >> 19);
378+
for (x=0; x<pDraw->iWidth; x++) {
379+
int a;
380+
c = *s++;
381+
a = pDraw->pPalette[768+c]; // get alpha
382+
if (a == 0) { // pure BGColor
383+
usPixel = u16Clr;
384+
} else if (a == 255) { // opaque
385+
pPal = &pDraw->pPalette[c * 3];
386+
usPixel = ((pPal[2] * a) >> 11); // blue
387+
usPixel |= (((pPal[1] * a) >> 10) << 5); // green
388+
usPixel |= (((pPal[0] * a) >> 11) << 11); // red
389+
} else { // need to mix the bg & fg colors
390+
391+
pPal = &pDraw->pPalette[c * 3];
392+
usPixel = ((((pPal[2] * a) + (b_b * (255-a)))) >> 11); // blue
393+
usPixel |= ((((pPal[1] * a) + (b_g * (255-a)))>> 10) << 5); // green
394+
usPixel |= ((((pPal[0] * a) + (b_r * (255-a)))>> 11) << 11); // red
395+
} // need to mix with alpha
396+
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
397+
usPixel = __builtin_bswap16(usPixel);
398+
*pDest++ = usPixel;
399+
} // for x
400+
} else { // alpha 0 = black
401+
for (x=0; x<pDraw->iWidth; x++) {
402+
int a;
403+
c = *s++;
404+
a = pDraw->pPalette[768+c]; // get alpha
405+
pPal = &pDraw->pPalette[c * 3];
406+
usPixel = ((pPal[2] * a) >> 11); // blue
407+
usPixel |= (((pPal[1] * a) >> 10) << 5); // green
408+
usPixel |= (((pPal[0] * a) >> 11) << 11); // red
409+
if (iEndiannes == PNG_RGB565_BIG_ENDIAN)
410+
usPixel = __builtin_bswap16(usPixel);
411+
*pDest++ = usPixel;
412+
} // for x
413+
}
361414
} else {
362415
for (x=0; x<pDraw->iWidth; x++) {
363416
c = *s++;

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